Fix testing on most recent Drupal core versions

Also found and reported 🐛 PHPStan baseline removed before generating a new one from test results Active .

I'd like to open a new MR here to test (and potentially fix) the phpstan problem.

That's good. The phpstan jobs now run as expected and report actual warnings.

Setting to NR as this change could be committed, and just to let you know, I'm not planning on working on the actual phpstan fixes. They could be done here or in a follow-up issue.

Thank you again. I will probably move the changes to another ticket since this task was about tests and the code was already released.