Update python-app.yml

.github/workflows/python-app.yml

@@ -18,7 +18,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v4
         with:
-            python-version: "3.8"
+            python-version: "3.9"
       - name: Build arc_omero
         run: |
           python -m venv test_env