[MNT] remove no longer existing jobs from required list in CI

[fkiraly]

There are a few jobs in openml that should be removed from being required, since they are no longer valid:

• jobs that no longer exist or run: docker, (windows-latest, Py, sk0.24.*, sk-only:false)
• jobs that relate to long-deprecated python versions (3.8 and 3.9)

Without this, not even maintainers can merge pull requests.

@PGijsbers, @joaquinvanschoren, would you kindly be able to fix, this is blocking us from using CI for testing.

To fix this, an admin or maintainer should go (on GitHub GUI) to:

Settings -> branches (left menu) -> main, edit -> scroll down to "Require status checks to pass before merging" and click the "X" next to the above.

While you are there, you could also go to the "general" pane and ensure checkmarks are like this:

Otherwise, PR may get merged as individual commits and mess up the main commit history. Squashing is an easy way to avoid conflicts and rebase accidents.

[fkiraly]

Temporarily fixed by #1572 which generates dummy jobs with the same name as the no longer existing required ones - the dummy jobs should be removed to close this issue.