Fix CI

[janjagusch]

This PR fixes two CI errors:

• It updates the black pre-commit hook and formats the source code according to the new black opinions. This avoids nasty CI errors as in https://github.com/mamba-org/quetz/runs/5837567998?check_suite_focus=true. Background on this error: Incompatible with click 8.1.0 (ImportError: cannot import name '_unicodefun' from 'click') psf/black#2964.
• It pins authlib=0.15.0 to avoid MismatchingStateError in the testing suite. Background on this error: CSRF Warning! State not equal in request and response lepture/authlib#376.

[codecov-commenter]

Codecov Report

Merging #513 (9bc5546) into main (b04fe03) will decrease coverage by 0.91%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #513      +/-   ##
==========================================
- Coverage   83.22%   82.31%   -0.92%     
==========================================
  Files          78       78              
  Lines        5891     5891              
==========================================
- Hits         4903     4849      -54     
- Misses        988     1042      +54     

Impacted Files	Coverage Δ
quetz/authentication/pam.py	82.71% <ø> (ø)
quetz/pkgstores.py	42.54% <0.00%> (-11.63%)	⬇️
quetz/channel_data.py	90.00% <0.00%> (-2.50%)	⬇️

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