Support streaming mlsum dataset
Support streaming mlsum dataset.

This PR:
- pins `fsspec` min version with fixed BlockSizeError: `fsspec[http]>=2021.11.1`
  - https://github.com/fsspec/filesystem_spec/pull/830
- unpins `s3fs==2021.08.1` to align it with `fsspec` requirement: `s3fs>=2021.11.1`
  > s3fs 2021.8.1 requires fsspec==2021.08.1
  - see discussion: https://github.com/huggingface/datasets/pull/2858/files#r700027326
- updates the following requirements to be compatible with the previous ones and one with each other:
  - `aiobotocore==1.4.2` to `aiobotocore>=2.0.1` (required by s3fs>=2021.11.1)
  - `boto3==1.17.106` to `boto3>=1.19.8` (to be compatible with aiobotocore>=2.0.1)
  - `botocore==1.20.106` to `botocore>=1.22.8` (to be compatible with aiobotocore and boto3)

Fix #4572.