TST: fix compatibility with pytest 8

[neutrinoceros]

This should resolve the current CI instability. (example logs)

For context, what I think is happening is that the pytest.warns context manager's behavior was changed in pytest 8.0. In older versions, all warnings other than the one we were checking for were silently swallowed, and now they're not. In this specific test, astropy would also emit some AstropyUserWarning(s), which we don't control but are pointing to the very same problem we're testing for, so we should just filter them explicitly.

[neutrinoceros]

there was another warning specificly in oldest deps, which took a bit longer to inspect. I think I fixed it but I'll undraft only when CI is actually green everywhere

[neutrinoceros]

For context, I tracked the numpy deprecation warning down to astroscrappy. This was fixed upstream in astropy/astroscrappy@e5c12fa (first published in v1.1.0)

I also threw in the --color=yes pytest flag while I was at it, as done in astropy, which helps reading logs in CI

[neutrinoceros]

btw Python 3.11 and 3.12 are not tested at all. I'll add them to the test matrix in a follow up PR just in case it uncovers incompatibilities and I need to fix those too.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.55%. Comparing base (649330c) to head (b962f56).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #820   +/-   ##
=======================================
  Coverage   97.55%   97.55%           
=======================================
  Files           9        9           
  Lines        1392     1392           
=======================================
  Hits         1358     1358           
  Misses         34       34           

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[mwcraig]

Thanks, @neutrinoceros!