Drop Python 3.9 support

[juhoinkinen]

Drops Annif's support for Python 3.9, rotates Python versions in CI/CD pipeline and updates Python version for Scrutinizer to 3.12.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.64%. Comparing base (bf802c7) to head (72a6303).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #849      +/-   ##
==========================================
+ Coverage   99.63%   99.64%   +0.01%     
==========================================
  Files          99       99              
  Lines        7349     7349              
==========================================
+ Hits         7322     7323       +1     
+ Misses         27       26       -1     

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[osma]

Codecov shows a number of indirect changes to coverage. Basically around 20 code lines related to backends that are not installed are not being covered by the tests. Why is that? Is it possible that all optional features get installed for all Python versions, or something along those lines?

[juhoinkinen]

When versions were rotated and new dependencies got installed to a Python version specific job, the old dependencies remained in cache, so all features were available.

I cleared the caches. Now indirect changes actually increases with few lines (increase is surprising, why?).

[osma]

Indeed that's a bit mysterious. I can't think of a reason for the change.

[osma]

lgtm