Reformat source code with latest Black

[soininen]

This PR formats the code with black version 24.4.2.

No functional changes whatsoever.

Re spine-tools/Spine-Toolbox#2733

Checklist before merging

• Code has been formatted by black

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 78.25%. Comparing base (67cf3b7) to head (2c0e9ec).

Files	Patch %	Lines
spinedb_api/graph_layout_generator.py	0.00%	1 Missing ⚠️
spinedb_api/spine_io/gdx_utils.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #394   +/-   ##
=======================================
  Coverage   78.25%   78.25%           
=======================================
  Files          75       75           
  Lines        9511     9511           
  Branches     2014     2014           
=======================================
  Hits         7443     7443           
  Misses       1735     1735           
  Partials      333      333           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.