Bump peaceiris/actions-gh-pages from 3.9.3 to 4.0.0

Bumps [peaceiris/actions-gh-pages](https://github.com/peaceiris/actions-gh-pages) from 3.9.3 to 4.0.0.
- [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@v3.9.3...v4.0.0)

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

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

.github/workflows/deploy-book.yaml

@@ -66,7 +66,7 @@ jobs:
       # Push the book's HTML to github-pages
       - name: Deploy to GitHub pages
         if: github.ref == 'refs/heads/main'
-        uses: peaceiris/actions-gh-pages@v3.9.3
+        uses: peaceiris/actions-gh-pages@v4.0.0
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: ./_build/html

.github/workflows/deploy-preview.yaml

@@ -116,7 +116,7 @@ jobs:
           github.event.workflow_run.conclusion == 'success'
           && steps.find-pull-request.outputs.number != ''
           && steps.fc.outputs.comment-id != ''
-        uses: peaceiris/actions-gh-pages@v3.9.3
+        uses: peaceiris/actions-gh-pages@v4.0.0
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
           publish_dir: _build/html