chore(python): Update the python version in docs presubmit to use 3.10

[parthea]

The docs nox session requires Python 3.10 but the Github action runs with Python 3.9

synthtool/synthtool/gcp/templates/python_library/noxfile.py.j2

Lines 358 to 359 in e808c98

	@nox.session(python="3.10")
	def docs(session):

synthtool/synthtool/gcp/templates/python_library/.github/workflows/docs.yml

Lines 6 to 15 in e808c98

	jobs:
	docs:
	runs-on: ubuntu-latest
	steps:
	- name: Checkout
	uses: actions/checkout@v4
	- name: Setup Python
	uses: actions/setup-python@v5
	with:
	python-version: "3.9"