PR #13704 proposes a breaking change, so I figure we should agree that the next release can be a major before we merge it.

pytest 8.0.0 was released on 2024-01-27, and a major after 4 minors is our usual pattern.

I also propose we drop Python 3.9 since it will become end-of-life in October (source).

I can handle the necessary preparations and the release, aiming for end of September/start of October.