reddit_tifu dataset: Checksums didn't match for dataset source files
Hi @XingxingZhang, 

We have already fixed this. You should update `datasets` version to at least 1.18.4:
```shell
pip install -U datasets
```
And then force the redownload:
```python
load_dataset("...", download_mode="force_redownload")
```

Duplicate of:
- #3773
## Describe the bug
When loading the reddit_tifu dataset, it throws the exception "Checksums didn't match for dataset source files"


## Steps to reproduce the bug
```python
import datasets
from datasets import load_dataset

print(datasets.__version__)

# load_dataset('billsum')

load_dataset('reddit_tifu', 'short')
```


## Environment info
<!-- You can run the command `datasets-cli env` and copy-and-paste its output below. -->
- `datasets` version: 1.17.0
- Platform: mac os
- Python version: Python 3.7.6
- PyArrow version: 3.0.0

reddit_tifu dataset: Checksums didn't match for dataset source files 
 ## Describe the bug
When loading the reddit_tifu dataset, it throws the exception "Checksums didn't match for dataset source files"


## Steps to reproduce the bug
```python
import datasets
from datasets import load_dataset

print(datasets.__version__)

# load_dataset('billsum')

load_dataset('reddit_tifu', 'short')
```


## Environment info
<!-- You can run the command `datasets-cli env` and copy-and-paste its output below. -->
- `datasets` version: 1.17.0
- Platform: mac os
- Python version: Python 3.7.6
- PyArrow version: 3.0.0
 
 Hi @XingxingZhang, 

We have already fixed this. You should update `datasets` version to at least 1.18.4:
```shell
pip install -U datasets
```
And then force the redownload:
```python
load_dataset("...", download_mode="force_redownload")
```

Duplicate of:
- #3773