Consider switching back to `pip-audit`

[woodruffw]

We switched to osv-scanner because of a significant performance regression in pip-audit. That regression has now been fixed with the 2.6.0 release, so we should consider switching back.

Low priority since the performance of osv-scanner is probably good enough, and the data quality should be similar.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.

[github-actions]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs.