Update datasets to 2.20.0
Update datasets to 2.20.0.

This PR is intended to address the CI errors raised by this update, as a first step before:
- #3037

Fixes after the update of `datasets`:
- Pass `trust_remote_code=True` for script dataset: 227f2c4
- Use JSON-Lines (instead of JSON) dataset in `test_statistics_endpoint` to avoid pandas bug that downcasts float to int column: a86d040 
Update datasets to 2.20.0: Update datasets to 2.20.0.

This PR is intended to address the CI errors raised by this update, as a first step before:
- #3037

Fixes after the update of `datasets`:
- Pass `trust_remote_code=True` for script dataset: 227f2c4
- Use JSON-Lines (instead of JSON) dataset in `test_statistics_endpoint` to avoid pandas bug that downcasts float to int column: a86d040 