build(deps): bump actions/setup-python from 3 to 4 (#947)

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>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

.github/workflows/on-merge-to-main.yml

@@ -61,7 +61,7 @@ jobs:
     # Generate documentation
     #########################
     - name: Set up Python
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: '3.8'
     - name: Install doc generation dependencies

.github/workflows/on-release-prod.yml

@@ -66,7 +66,7 @@ jobs:
       # Generate documentation
       #########################
     - name: Set up Python
-      uses: actions/setup-python@v3
+      uses: actions/setup-python@v4
       with:
         python-version: '3.8'
     - name: Set RELEASE_VERSION env var