TST: pytest-dev gives 3 errors in devinfra jobs from suspicious skips #20830

• astropy/cosmology/_src/tests/flrw/test_flrw.py::TestFLRW::test_luminosity_distance_pandas - pytest.PytestWarning: The reason 'w(z) is abstract' of pytest.mark.skip looks like a condition. Did you mean pytest.mark.skipif?
• astropy/cosmology/_src/tests/io/test_mapping.py::TestToFromMapping::test_fromformat_subclass_partial_info_mapping - pytest.PytestWarning: The reason 'N/A' of pytest.mark.skip looks like a condition. Did you mean pytest.mark.skipif?
• astropy/modeling/tests/test_quantities_fitting.py::test_compound_fitting_with_units[LevMarLSQFitter] - pytest.PytestWarning: The reason 'Flaky and ill-conditioned' of pytest.mark.skip looks like a condition. Did you mean pytest.mark.skipif?

I see #20813 is addressing the 2 cosmology ones, but are you also planning on addressing the modeling test, @neutrinoceros ?