Use recent Python version in workflow

.github/workflows/validation.yml

@@ -17,10 +17,10 @@ jobs:
     steps:
     - uses: actions/checkout@v2
 
-    - name: Set up Python 3.9
+    - name: Set up Python 3.11
       uses: actions/setup-python@v1
       with:
-        python-version: 3.9
+        python-version: 3.11
 
     - name: Install dependencies
       run: pip install -r requirements.txt