Issue: Checksum error for glue sst2, stsb, rte etc datasets

## Describe the bug
Checksum error for glue sst2, stsb, rte etc datasets

## Steps to reproduce the bug
```python
>>> nlp.load_dataset('glue', 'sst2')
Downloading and preparing dataset glue/sst2 (download: 7.09 MiB, generated: 4.81 MiB, post-processed: Unknown sizetotal: 11.90 MiB) to 
Downloading: 100%|████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 73.0/73.0 [00:00<00:00, 18.2kB/s]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Python/3.8/lib/python/site-packages/nlp/load.py", line 548, in load_dataset
    builder_instance.download_and_prepare(
  File "/Library/Python/3.8/lib/python/site-packages/nlp/builder.py", line 462, in download_and_prepare
    self._download_and_prepare(
  File "/Library/Python/3.8/lib/python/site-packages/nlp/builder.py", line 521, in _download_and_prepare
    verify_checksums(
  File "/Library/Python/3.8/lib/python/site-packages/nlp/utils/info_utils.py", line 38, in verify_checksums
    raise NonMatchingChecksumError(error_msg + str(bad_urls))
nlp.utils.info_utils.NonMatchingChecksumError: Checksums didn't match for dataset source files:
['https://firebasestorage.googleapis.com/v0/b/mtl-sentence-representations.appspot.com/o/data%2FSST-2.zip?alt=media&token=aabc5f6b-e466-44a2-b9b4-cf6337f84ac8']
```

## Expected results
dataset load should succeed without checksum error.

## Actual results
```
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Python/3.8/lib/python/site-packages/nlp/load.py", line 548, in load_dataset
    builder_instance.download_and_prepare(
  File "/Library/Python/3.8/lib/python/site-packages/nlp/builder.py", line 462, in download_and_prepare
    self._download_and_prepare(
  File "/Library/Python/3.8/lib/python/site-packages/nlp/builder.py", line 521, in _download_and_prepare
    verify_checksums(
  File "/Library/Python/3.8/lib/python/site-packages/nlp/utils/info_utils.py", line 38, in verify_checksums
    raise NonMatchingChecksumError(error_msg + str(bad_urls))
nlp.utils.info_utils.NonMatchingChecksumError: Checksums didn't match for dataset source files:
['https://firebasestorage.googleapis.com/v0/b/mtl-sentence-representations.appspot.com/o/data%2FSST-2.zip?alt=media&token=aabc5f6b-e466-44a2-b9b4-cf6337f84ac8']
```
## Environment info
- `datasets` version: '1.18.3'
- Platform: Mac OS
- Python version: Python 3.8.9
- PyArrow version: '7.0.0'


Comments:
Hi, @ravindra-ut.

I'm sorry but I can't reproduce your problem:
```python
In [1]: from datasets import load_dataset

In [2]: ds = load_dataset("glue", "sst2")
Downloading builder script: 28.8kB [00:00, 11.6MB/s]                                                                                                                                                       
Downloading metadata: 28.7kB [00:00, 12.9MB/s]                                                                                                                                                             
Downloading and preparing dataset glue/sst2 (download: 7.09 MiB, generated: 4.81 MiB, post-processed: Unknown size, total: 11.90 MiB) to .../.cache/huggingface/datasets/glue/sst2/1.0.0/dacbe3125aa31d7f70367a07a8a9e72a5a0bfeb5fc42e75c9db75b96da6053ad...
Downloading data: 100%|███████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 7.44M/7.44M [00:01<00:00, 5.82MB/s]
Dataset glue downloaded and prepared to .../.cache/huggingface/datasets/glue/sst2/1.0.0/dacbe3125aa31d7f70367a07a8a9e72a5a0bfeb5fc42e75c9db75b96da6053ad. Subsequent calls will reuse this data.  
100%|███████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 3/3 [00:00<00:00, 895.96it/s]

In [3]: ds
Out[2]: 
DatasetDict({
    train: Dataset({
        features: ['sentence', 'label', 'idx'],
        num_rows: 67349
    })
    validation: Dataset({
        features: ['sentence', 'label', 'idx'],
        num_rows: 872
    })
    test: Dataset({
        features: ['sentence', 'label', 'idx'],
        num_rows: 1821
    })
})
``` 

Moreover, I see in your traceback that your error was for an URL at https://firebasestorage.googleapis.com
However, the URLs were updated on Sep 16, 2020 (`datasets` version 1.0.2) to https://dl.fbaipublicfiles.com: https://github.com/huggingface/datasets/commit/2f03041a21c03abaececb911760c3fe4f420c229

Could you please try to update `datasets`
```shell
pip install -U datasets
```
and then force redownload
```python
ds = load_dataset("glue", "sst2", download_mode="force_redownload")
```
to update the cache?

Please, feel free to reopen this issue if the problem persists.