chore(deps): bump peaceiris/actions-gh-pages from 3 to 4

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

@@ -68,7 +68,7 @@ jobs:
         touch docs/_build/.nojekyll
         cp docs/redirect.html docs/_build/index.html
     - name: Publish docs to gh-pages
-      uses: peaceiris/actions-gh-pages@v3
+      uses: peaceiris/actions-gh-pages@v4
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
         publish_dir: docs/_build