Bump peaceiris/actions-gh-pages from 3 to 4 in the actions group

Bumps the actions group with 1 update: [peaceiris/actions-gh-pages](https://github.com/peaceiris/actions-gh-pages).


Updates `peaceiris/actions-gh-pages` from 3 to 4
- [Release notes](https://github.com/peaceiris/actions-gh-pages/releases)
- [Changelog](https://github.com/peaceiris/actions-gh-pages/blob/main/CHANGELOG.md)
- [Commits](peaceiris/actions-gh-pages@v3...v4)

---
updated-dependencies:
- dependency-name: peaceiris/actions-gh-pages
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: actions
...

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

.github/workflows/documentation.yml

@@ -27,7 +27,7 @@ jobs:
  run: |
  sphinx-build docs/source/ docs/build
  - name: Deploy
- uses: peaceiris/actions-gh-pages@v3
+ uses: peaceiris/actions-gh-pages@v4
  if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
  with:
  publish_branch: gh-pages