Ergast Deprecation Warn

[pbulsink]

Closes #221

New behaviour is:

• a note in the Readme that changes will come at the end of 2024.
• Soft deprecation in get_ergast_content() which shouldn't affect anyone not calling that function directly.

By September 2024 (at the latest), we should deprecate_warn() that function to notify all users to look for a new version soon, and once an alternative is available we move to the new back-end data source and deprecate_stop() the Ergast link.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (9ca668a) 60.60% compared to head (8743e68) 60.86%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #222 +/- ## ========================================== + Coverage 60.60% 60.86% +0.26% ========================================== Files 19 19 Lines 594 598 +4 ========================================== + Hits 360 364 +4 Misses 234 234 ```

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