coqa NonMatchingChecksumError
Hi, still not able to reproduce the issue with `coqa`. If you still have this issue, could you please run these additional commands ?
```python
>>> import os
>>> from hashlib import md5
>>> from datasets.utils import DownloadManager, DownloadConfig
>>> path = DownloadManager(download_config=DownloadConfig(use_etag=False)).download("https://nlp.stanford.edu/data/coqa/coqa-dev-v1.0.json")  # it returns the cached file
>>> os.path.getsize(path)
9090845
>>> m = md5()
>>> m.update(open(path, "rb").read())
>>> m.hexdigest()
`95d427588e3733e4ebec55f6938dbba6`
>>> open(path).read(500)
'{\n  "version": "1.0",\n  "data": [\n    {\n      "source": "mctest",\n      "id": "3dr23u6we5exclen4th8uq9rb42tel",\n      "filename": "mc160.test.41",\n      "story": "Once upon a time, in a barn near a farm house, there lived a little white kitten named Cotton. Cotton lived high up in a nice warm place above the barn where all of the farmer\'s horses slept. But Cotton wasn\'t alone in her little home above the barn, oh no. She shared her hay bed with her mommy and 5 other sisters. All of her sisters w'
```

This way we can know whether you downloaded a corrupted file or an error file that could cause the `NonMatchingChecksumError` error to happen
```
>>> from datasets import load_dataset
>>> dataset = load_dataset("coqa")
Downloading: 3.82kB [00:00, 1.26MB/s]                                                                                                                                                                                                                       
Downloading: 1.79kB [00:00, 733kB/s]                                                                                                                                                                                                                        
Using custom data configuration default
Downloading and preparing dataset coqa/default (download: 55.40 MiB, generated: 18.35 MiB, post-processed: Unknown size, total: 73.75 MiB) to /Users/zhaofengw/.cache/huggingface/datasets/coqa/default/1.0.0/553ce70bfdcd15ff4b5f4abc4fc2f37137139cde1f58f4f60384a53a327716f0...
Downloading: 100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 222/222 [00:00<00:00, 1.38MB/s]
Downloading: 100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 222/222 [00:00<00:00, 1.32MB/s]
100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 2/2 [00:01<00:00,  1.91it/s]
100%|███████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 2/2 [00:00<00:00, 1117.44it/s]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/zhaofengw/miniconda3/lib/python3.9/site-packages/datasets/load.py", line 1632, in load_dataset
    builder_instance.download_and_prepare(
  File "/Users/zhaofengw/miniconda3/lib/python3.9/site-packages/datasets/builder.py", line 607, in download_and_prepare
    self._download_and_prepare(
  File "/Users/zhaofengw/miniconda3/lib/python3.9/site-packages/datasets/builder.py", line 679, in _download_and_prepare
    verify_checksums(
  File "/Users/zhaofengw/miniconda3/lib/python3.9/site-packages/datasets/utils/info_utils.py", line 40, in verify_checksums
    raise NonMatchingChecksumError(error_msg + str(bad_urls))
datasets.utils.info_utils.NonMatchingChecksumError: Checksums didn't match for dataset source files:
['https://nlp.stanford.edu/data/coqa/coqa-train-v1.0.json', 'https://nlp.stanford.edu/data/coqa/coqa-dev-v1.0.json']
```
coqa NonMatchingChecksumError 
 ```
>>> from datasets import load_dataset
>>> dataset = load_dataset("coqa")
Downloading: 3.82kB [00:00, 1.26MB/s]                                                                                                                                                                                                                       
Downloading: 1.79kB [00:00, 733kB/s]                                                                                                                                                                                                                        
Using custom data configuration default
Downloading and preparing dataset coqa/default (download: 55.40 MiB, generated: 18.35 MiB, post-processed: Unknown size, total: 73.75 MiB) to /Users/zhaofengw/.cache/huggingface/datasets/coqa/default/1.0.0/553ce70bfdcd15ff4b5f4abc4fc2f37137139cde1f58f4f60384a53a327716f0...
Downloading: 100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 222/222 [00:00<00:00, 1.38MB/s]
Downloading: 100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 222/222 [00:00<00:00, 1.32MB/s]
100%|█████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 2/2 [00:01<00:00,  1.91it/s]
100%|███████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 2/2 [00:00<00:00, 1117.44it/s]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/zhaofengw/miniconda3/lib/python3.9/site-packages/datasets/load.py", line 1632, in load_dataset
    builder_instance.download_and_prepare(
  File "/Users/zhaofengw/miniconda3/lib/python3.9/site-packages/datasets/builder.py", line 607, in download_and_prepare
    self._download_and_prepare(
  File "/Users/zhaofengw/miniconda3/lib/python3.9/site-packages/datasets/builder.py", line 679, in _download_and_prepare
    verify_checksums(
  File "/Users/zhaofengw/miniconda3/lib/python3.9/site-packages/datasets/utils/info_utils.py", line 40, in verify_checksums
    raise NonMatchingChecksumError(error_msg + str(bad_urls))
datasets.utils.info_utils.NonMatchingChecksumError: Checksums didn't match for dataset source files:
['https://nlp.stanford.edu/data/coqa/coqa-train-v1.0.json', 'https://nlp.stanford.edu/data/coqa/coqa-dev-v1.0.json']
``` 
 Hi, still not able to reproduce the issue with `coqa`. If you still have this issue, could you please run these additional commands ?
```python
>>> import os
>>> from hashlib import md5
>>> from datasets.utils import DownloadManager, DownloadConfig
>>> path = DownloadManager(download_config=DownloadConfig(use_etag=False)).download("https://nlp.stanford.edu/data/coqa/coqa-dev-v1.0.json")  # it returns the cached file
>>> os.path.getsize(path)
9090845
>>> m = md5()
>>> m.update(open(path, "rb").read())
>>> m.hexdigest()
`95d427588e3733e4ebec55f6938dbba6`
>>> open(path).read(500)
'{\n  "version": "1.0",\n  "data": [\n    {\n      "source": "mctest",\n      "id": "3dr23u6we5exclen4th8uq9rb42tel",\n      "filename": "mc160.test.41",\n      "story": "Once upon a time, in a barn near a farm house, there lived a little white kitten named Cotton. Cotton lived high up in a nice warm place above the barn where all of the farmer\'s horses slept. But Cotton wasn\'t alone in her little home above the barn, oh no. She shared her hay bed with her mommy and 5 other sisters. All of her sisters w'
```

This way we can know whether you downloaded a corrupted file or an error file that could cause the `NonMatchingChecksumError` error to happen