simplify flake8 config, fix some complaints

[ThomasWaldmann]

No description provided.

[codecov-commenter]

Codecov Report

Merging #7740 (aa0d12a) into master (c0001fb) will decrease coverage by 0.03%.
The diff coverage is 58.82%.

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@@            Coverage Diff             @@
##           master    #7740      +/-   ##
==========================================
- Coverage   83.68%   83.66%   -0.03%     
==========================================
  Files          66       66              
  Lines       11918    11915       -3     
  Branches     2159     2159              
==========================================
- Hits         9974     9969       -5     
- Misses       1369     1371       +2     
  Partials      575      575              

Files Changed	Coverage Δ
src/borg/archiver/__init__.py	85.53% <0.00%> (ø)
src/borg/archiver/_common.py	90.65% <ø> (ø)
src/borg/archiver/config_cmd.py	61.41% <0.00%> (ø)
src/borg/archiver/rlist_cmd.py	100.00% <ø> (ø)
src/borg/helpers/misc.py	78.12% <0.00%> (-0.95%)	⬇️
src/borg/helpers/shellpattern.py	94.20% <ø> (ø)
src/borg/locking.py	85.57% <0.00%> (ø)
src/borg/manifest.py	93.13% <ø> (ø)
src/borg/remote.py	83.11% <ø> (ø)
src/borg/repository.py	83.27% <ø> (ø)
... and 7 more

[ThomasWaldmann]

@bigtedde done!