chore: update docfx minimum Python version (#545)

* chore: update docfx minimum Python version

Source-Link: https://github.com/googleapis/synthtool/commit/bc07fd415c39853b382bcf8315f8eeacdf334055
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:30470597773378105e239b59fce8eb27cc97375580d592699206d17d117143d0

* update docfx nox session to use python 3.10

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>
Co-authored-by: Anthonios Partheniou <partheniou@google.com>
diff --git a/.github/.OwlBot.lock.yaml b/.github/.OwlBot.lock.yaml
index 7f291db..ec696b5 100644
--- a/.github/.OwlBot.lock.yaml
+++ b/.github/.OwlBot.lock.yaml
@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
-  digest: sha256:4f9b3b106ad0beafc2c8a415e3f62c1a0cc23cabea115dbe841b848f581cfe99
-# created: 2023-10-18T20:26:37.410353675Z
+  digest: sha256:30470597773378105e239b59fce8eb27cc97375580d592699206d17d117143d0
+# created: 2023-11-03T00:57:07.335914631Z
diff --git a/.github/workflows/docs.yml b/.github/workflows/docs.yml
index e97d89e..221806c 100644
--- a/.github/workflows/docs.yml
+++ b/.github/workflows/docs.yml
@@ -28,7 +28,7 @@
     - name: Setup Python
       uses: actions/setup-python@v4
       with:
-        python-version: "3.9"
+        python-version: "3.10"
     - name: Install nox
       run: |
         python -m pip install --upgrade setuptools pip wheel
diff --git a/noxfile.py b/noxfile.py
index 84abb49..82ea266 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -232,7 +232,7 @@
     )
 
 
-@nox.session(python="3.9")
+@nox.session(python="3.10")
 def docfx(session):
     """Build the docfx yaml files for this library."""