Bump peaceiris/actions-gh-pages from 3.6.1 to 3.9.3 (#29)

Bumps [peaceiris/actions-gh-pages](https://github.com/peaceiris/actions-gh-pages) from 3.6.1 to 3.9.3.
- [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@v3.6.1...v3.9.3)

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

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

.github/workflows/deploy-book.yaml

@@ -28,7 +28,7 @@ jobs:
           jupyter-book build notebooks
       # Deploy the book's HTML to gh-pages branch
       - name: GitHub Pages action
-        uses: peaceiris/actions-gh-pages@v3.6.1
+        uses: peaceiris/actions-gh-pages@v3.9.3
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: notebooks/_build/html