Tests with pdb and coverage are failing.

coverage was pinned to <= 6.4 in #283. This blocks us from testing pytask with Python 3.11.

So, we are going to xfail the problematic tests in #307.

Other related issues

- Same issue for pytest: `https://github.com/pytest-dev/pytest/issues/10042`
- Issue raised for coverage: `https://github.com/nedbat/coveragepy/issues/1402`