Use Python 3.12 in CI (3.8 unavailable on ubuntu-26.04)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Author: denis-yuen

.github/workflows/maven.yml

@@ -22,7 +22,7 @@ jobs:
      - name: Set up Python
        uses: actions/setup-python@v7
        with:
-         python-version: 3.8
+         python-version: 3.12
      - name: Install dependencies
        run: |
          python -m pip install --upgrade pip