Remove the pytest-timeout usage

[matrss]

I'd argue that using pytest-timeout does not give us any benefit:

1. As discovered in Run the test suite in a random order #2287 (comment) it seems like its timeout is actively stopping test runs on macOS 13 that genuinely need more time, since the runners are just very slow.
2. Most of the time where it would be useful (e.g. when some remaining Qt window blocks further test execution) it actually fails to do its job, in my experience (i.e. the GitHub Actions timeout is reached instead).

Therefore I think we could get rid of it.