Lift Python version upper limit

[soininen]

This PR removes the Python version restriction < 3.12 from Spine-Items.

Re spine-tools/Spine-Toolbox#2522

Checklist before merging

• Unit tests pass

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 62.71%. Comparing base (39acd53) to head (1d4c9d4).

❗ Current head 1d4c9d4 differs from pull request most recent head 31f0df7. Consider uploading reports for the commit 31f0df7 to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #211   +/-   ##
=======================================
  Coverage   62.71%   62.71%           
=======================================
  Files         190      190           
  Lines       17909    17909           
  Branches     2951     2951           
=======================================
  Hits        11231    11231           
  Misses       6076     6076           
  Partials      602      602           

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