Use Python 3.9 for test workflow

Author: RalfG

.github/workflows/test.yml

@@ -13,10 +13,10 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
-      - name: Set up Python 3.8
+      - name: Set up Python 3.9
         uses: actions/setup-python@v5
         with:
-          python-version: "3.8"
+          python-version: "3.9"
 
       - name: Install dependencies
         run: |