chore(ci): update docs pipeline python version (googleapis#127)

Author: averikitsch

.github/workflows/docs.yml

@@ -12,7 +12,7 @@ jobs:
     - name: Setup Python
       uses: actions/setup-python@82c7e631bb3cdc910f68e0081d67478d79c6982d # v5
       with:
-        python-version: "3.9"
+        python-version: "3.10"
     - name: Install nox
       run: |
         python -m pip install --upgrade setuptools pip wheel
@@ -35,4 +35,4 @@ jobs:
         python -m pip install nox
     - name: Run docfx
       run: |
-        nox -s docfx
+        nox -s docfx