use python3.9

Signed-off-by: YunLiu <55491388+KumoLiu@users.noreply.github.com>

.github/workflows/pythonapp.yml

@@ -130,10 +130,10 @@ jobs:
     - uses: actions/checkout@v4
       with:
         fetch-depth: 0
-    - 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: cache weekly timestamp
       id: pip-cache
       run: |