Over the last month we have been experience strange errors with code coverage measurements on GitHub actions workflows, specifically related to Python 3.12. We thought we fixed these issues by uprading to the latest coverage modules, but it still seems like an intermittent issue (related to timing or race conditions specifically under 3.12). We also see that running the test suite on Python 3.12 takes significantly longer than other versions.

I suggest we simply remove Python 3.12 from our test matrix.

Rationale:

1. The test matrix includes 3.11 and 3.13, it is therefore unlikely we should experience test failures that are specific to only the release in between them.
2. We use Debian in our own production environments, therefore we will never run NAV on Python 3.12 in production (Debian 12 provides Python 3.11, Debian 13 provides Python 3.13).