[test] Addresses a Hypothesis health check that leads to failing tests.

Class-based tests that inherit a Hypothesis test case emit a Hypothesis health check warning starting from hypothesis-6.83.2 [0][1]. This is due to inherited tests being run by different Hypothesis executors and may cause issues when replaying examples [2].

Inheriting Hypothesis tests in subclasses is clearly not wanted, so it makes sense to remove the pytest-asyncio test that tests for this feature.

[0] https://hypothesis.readthedocs.io/en/latest/changes.html#v6-83-2
[1] HypothesisWorks/hypothesis#3720
[2] HypothesisWorks/hypothesis#3446

Signed-off-by: Michael Seifert <m.seifert@digitalernachschub.de>