Bump peaceiris/actions-gh-pages from 3 to 4 in the actions group (#735)

Bumps the actions group with 1 update: [peaceiris/actions-gh-pages](https://github.com/peaceiris/actions-gh-pages).


Updates `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
  dependency-group: actions
...

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

Author: dependabot[bot]

.github/workflows/pages.yml

@@ -41,7 +41,7 @@ jobs:
           touch build/html/.nojekyll
 
       - name: Deploy
-        uses: peaceiris/actions-gh-pages@v3
+        uses: peaceiris/actions-gh-pages@v4
         with:
           deploy_key: ${{ secrets.ACTIONS_DEPLOY_KEY }}
           external_repository: scipy-lectures/lectures.scientific-python.org