Use Python 3.12 to combine coverage

Author: adamchainz

.github/workflows/main.yml

@@ -57,7 +57,7 @@ jobs:
 
       - uses: actions/setup-python@v5
         with:
-          python-version: '3.11'
+          python-version: '3.12'
 
       - name: Install dependencies
         run: python -m pip install --upgrade coverage[toml]