Fix runner version to macos-13, as setup-python only support >=3.11 on osx 14

[robtaylor]

This is a limitation in setup-python, and a quick fix.

I think a better solution would be to use matrix for the os's and then use exclude for unsupported versions and possibly also use poetry environments for the different python versions, though this would be a bigger change to the CI.
Let me know if that would be of interest.

[codecov-commenter]

⚠️ Please install the to ensure uploads and comments are reliably processed by Codecov.

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.32%. Comparing base (fe8fc8d) to head (55a1a5e).
Report is 30 commits behind head on develop.

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #663   +/-   ##
========================================
  Coverage    96.32%   96.32%           
========================================
  Files           41       41           
  Lines         5218     5218           
  Branches       976      976           
========================================
  Hits          5026     5026           
  Misses         120      120           
  Partials        72       72           

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