Reverts #3953. Due to the change, GitHub Actions stopped running the checks while the checks are still marked as required. Tried this in #3959 (comment).

The documentation about this GitHub Actions behavior is https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/collaborating-on-repositories-with-code-quality-features/troubleshooting-required-status-checks#handling-skipped-but-required-checks :

If a workflow is skipped due to path filtering, branch filtering or a commit message, then checks associated with that workflow will remain in a "Pending" state. A pull request that requires those checks to be successful will be blocked from merging.

If, however, a job within a workflow is skipped due to a conditional, it will report its status as "Success". For more information, see Using conditions to control job execution.

I didn't find usages of a file path filter in the condition of a job within a workflow.

https://github.com/googleapis/sdk-platform-java/blob/main/.github/workflows/verify_library_generation.yaml#L8 is is a good example how to skip the main job library-generation-unit-tests, by introducing the should-run-library-generation-tests job.