CI is no longer running against pre-release pytest

Hi! Thanks for the nice extension.

I noticed PR #26009 pinned pytest to <8.1 in build/test-requirements.txt to avoid fixing a bug with the test configuration for pytest-black in 9.1 and above.

However, this defeats the purpose of the pytest@pre-release workflow. Now when that workflow is run, the pytest pre-release is installed, and then it's subsequently reverted back to 8.0.2. Example here: