Use Python 3.9

Author: methane

.github/workflows/django.yaml

@@ -20,10 +20,10 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-pip-
 
-      - name: Set up Python 3.10
+      - name: Set up Python
         uses: actions/setup-python@v2
         with:
-          python-version: "3.10"
+          python-version: "3.9"
 
       - uses: actions/checkout@v2
         with: