Bump actions/setup-python from 3 to 4 (kubernetes-sigs#74)

* Bump actions/setup-python from 3 to 4

Bumps [actions/setup-python](https://github.com/actions/setup-python) from 3 to 4.
- [Release notes](https://github.com/actions/setup-python/releases)
- [Commits](actions/setup-python@v3...v4)

---
updated-dependencies:
- dependency-name: actions/setup-python
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

* Set the python version.

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Quentin Barrand <quentin@quba.fr>

.github/workflows/docs.yaml

@@ -10,9 +10,10 @@ jobs:
     steps:
       - uses: actions/checkout@v3
 
-      - uses: actions/setup-python@v3
+      - uses: actions/setup-python@v4
         with:
           cache: pip
+          python-version: 3.x
 
       - name: Install mkdocs
         run: pip install -r docs/requirements.txt