Migrate to flake8 5.0.0 compatible config

[eivindjahren]

Fixes the build by migrating flake8 setup. See PyCQA/flake8#1630

Pre review checklist

• Added appropriate release note label
• PR title captures the intent of the changes, and is fitting for release notes.
• Commit history is consistent and clean, in line with the contribution guidelines.

Adding labels helps the maintainers when writing release notes. This is the list of release note labels.

[codecov-commenter]

Codecov Report

Merging #3661 (a4535d5) into main (79c44bd) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #3661      +/-   ##
==========================================
- Coverage   64.51%   64.50%   -0.01%     
==========================================
  Files         592      592              
  Lines       46159    46159              
  Branches     4161     4161              
==========================================
- Hits        29778    29774       -4     
- Misses      15037    15041       +4     
  Partials     1344     1344              

Impacted Files	Coverage Δ
src/res/job_queue/forward_model_status.py	88.60% <0.00%> (-5.07%)	⬇️

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