Merge pull request #435 from light-curve/ci-roll-back-coverage-to-3.12

CI: Roll-back coverage python to 3.12

Author: hombit

.github/workflows/test.yml

@@ -107,7 +107,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v5
         with:
-          python-version: "3.13"
+          python-version: "3.12"
       - name: Install build deps
         run: pip install "${{ needs.py_build_deps.outputs.output }}"
       - name: Install system dependencies