Clean up pre-commit

[blink1073]

• Make the non-automatic hooks manual and run on CI
• Remove unused workflow
• Update contributing docs

[codecov-commenter]

Codecov Report

Merging #782 (18c2a92) into main (77be2f5) will increase coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #782      +/-   ##
==========================================
+ Coverage   70.30%   70.39%   +0.09%     
==========================================
  Files          62       62              
  Lines        7554     7554              
  Branches     1248     1248              
==========================================
+ Hits         5311     5318       +7     
+ Misses       1860     1851       -9     
- Partials      383      385       +2     

Impacted Files	Coverage Δ
jupyter_server/services/kernels/kernelmanager.py	81.66% <0.00%> (+2.33%)	⬆️

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