ci: bump peaceiris/actions-gh-pages from v3 to v3.8.0 (#1888)

Bumps [peaceiris/actions-gh-pages](https://github.com/peaceiris/actions-gh-pages) from v3 to v3.8.0.
- [Release notes](https://github.com/peaceiris/actions-gh-pages/releases)
- [Changelog](https://github.com/peaceiris/actions-gh-pages/blob/main/CHANGELOG.md)
- [Commits](https://github.com/peaceiris/actions-gh-pages/compare/v3...068dc23d9710f1ba62e86896f84735d869951305)

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

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

.github/workflows/github_pages.yml

@@ -22,7 +22,7 @@ jobs:
         nix-build -A docs.html
         cp -r result/share/doc/home-manager public
     - name: Deploy
-      uses: peaceiris/actions-gh-pages@v3
+      uses: peaceiris/actions-gh-pages@v3.8.0
       with:
         github_token: ${{ secrets.GITHUB_TOKEN }}
         publish_dir: ./public