Getting configs names takes too long

## Steps to reproduce the bug
```python
from datasets import get_dataset_config_names
get_dataset_config_names("allenai/c4")
```

## Expected results

I would expect to get the answer quickly, at least in less than 10s

## Actual results

It takes about 45s on my environment

## Environment info

- `datasets` version: 1.16.1
- Platform: Linux-5.11.0-1022-aws-x86_64-with-glibc2.31
- Python version: 3.9.6
- PyArrow version: 4.0.1