Fix pass_env values cannot contain whitespace error in CI

[whimboo]

The CI actions for tox related jobs currently fail with:

     f"pass_env values cannot contain whitespace, use comma to have multiple values in a single line, "
tox.tox_env.errors.Fail: pass_env values cannot contain whitespace, use comma to have multiple values in a single line, invalid values found 'GITHUB_* CI'
Error: Process completed with exit code 1.

[whimboo]

The remaining issue is related to the removal of the LegacyVersion class in the packaging package. I'm going to fix that in a different PR.