Use python 3.9 (#892)

* Use python 3.10

* Remove changes

* Use 3.9 for docs

.github/workflows/docs.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v4
         with:
-          python-version: "3.10"
+          python-version: "3.9"
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip