MAINT add back pytest warnings plugin

[lesteve]

It was removed in #525, not sure whether this is still needed. At least locally the test pass on my machine with the changes in my PR.

Context: I was trying to trigger warnings due to pytest.warns(None) and pytest 7 and could not see them. https://docs.pytest.org/en/7.0.x/deprecations.html#using-pytest-warns-none

Probably it would be good to get the pytest.warns(None) replacement from #1264

[codecov]

Codecov Report

Base: 93.99% // Head: 93.96% // Decreases project coverage by -0.02% ⚠️

Coverage data is based on head (f497585) compared to base (a23427d).
Patch has no changes to coverable lines.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1337      +/-   ##
==========================================
- Coverage   93.99%   93.96%   -0.03%     
==========================================
  Files          52       52              
  Lines        7294     7294              
==========================================
- Hits         6856     6854       -2     
- Misses        438      440       +2     

Impacted Files	Coverage Δ
joblib/parallel.py	96.29% <0.00%> (-0.53%)	⬇️

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[ogrisel]

I agree we should report and progressively fix joblib to avoid triggering those warnings in the first place instead of hiding problems under the rug.

The random failures on macos have already been observed numerous times and are unrelated.

[ogrisel]

@lesteve feel free to takeover #1264 to finish it.