[3.11] gh-104629: Don't skip test_clinic if _testclinic is missing (GH-104630) (#104632)

gh-104629: Don't skip test_clinic if _testclinic is missing (GH-104630)

Just skip the tests that depend on the _testclinic extension module;
we can still run the Python tests.
(cherry picked from commit 86ee49f469b84e4b746526a00d8191d0e374a268)

Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>