build(deps): bump peaceiris/actions-gh-pages in /.github/workflows

Bumps [peaceiris/actions-gh-pages](https://github.com/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
...

Signed-off-by: dependabot[bot] <[email protected]>

.github/workflows/docs.yml

@@ -28,7 +28,7 @@ jobs:
             path: |
               docs/doxygen/output
       - name: Deploy documentation to gh-pages
-        uses: peaceiris/actions-gh-pages@v3
+        uses: peaceiris/actions-gh-pages@v4
         if: ${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }}
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}