Checksum error for kilt_task_wow
Using `dataset = load_dataset("kilt_tasks", "wow", ignore_verifications=True)` may fix it, but I do not think it is a elegant solution. Hi @slyviacassell, thanks for reporting.

Yes, there is an issue with the checksum verification. I'm fixing it.

And as you pointed out, in the meantime, you can circumvent the problem by passing `ignore_verifications=True`. 
## Describe the bug
Checksum failed when downloads kilt_tasks_wow. See error output for details.

## Steps to reproduce the bug
```python
import datasets
datasets.load_datasets('kilt_tasks','wow')
```

## Expected results
Download successful

## Actual results
```
Downloading and preparing dataset kilt_tasks/wow (download: 72.07 MiB, generated: 61.82 MiB, post-processed: Unknown size, total: 133.89 MiB) to /root/.cache/huggingface/datasets/kilt_tasks/wow/1.0.0/57dc8b2431e76637e0c6ef79689ca4af61ed3a330e2e0cd62c8971465a35db3a...
100%|████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 3/3 [00:00<00:00, 5121.25it/s]
100%|████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████| 3/3 [00:00<00:00, 1527.42it/s]
Traceback (most recent call last):
  File "kilt_wow.py", line 30, in <module>
    main()
  File "kilt_wow.py", line 27, in main
    train, dev, test = dataset.generate_k_shot_data(k=32, seed=seed, path="../data/")
  File "/workspace/projects/CrossFit/tasks/fewshot_gym_dataset.py", line 79, in generate_k_shot_data
    dataset = self.load_dataset()
  File "kilt_wow.py", line 21, in load_dataset
    return datasets.load_dataset('kilt_tasks','wow')
  File "/opt/conda/lib/python3.8/site-packages/datasets/load.py", line 1632, in load_dataset
    builder_instance.download_and_prepare(
  File "/opt/conda/lib/python3.8/site-packages/datasets/builder.py", line 607, in download_and_prepare
    self._download_and_prepare(
  File "/opt/conda/lib/python3.8/site-packages/datasets/builder.py", line 679, in _download_and_prepare
    verify_checksums(
  File "/opt/conda/lib/python3.8/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:
['http://dl.fbaipublicfiles.com/KILT/wow-train-kilt.jsonl', 'http://dl.fbaipublicfiles.com/KILT/wow-dev-kilt.jsonl']
```

## Environment info
<!-- You can run the command `datasets-cli env` and copy-and-paste its output below. -->
- `datasets` version: 1.15.1
- Platform: Linux-4.15.0-161-generic-x86_64-with-glibc2.10
- Python version: 3.8.3
- PyArrow version: 4.0.1
