Bump crazy-max/ghaction-github-pages from 2 to 4 (#108)

Bumps [crazy-max/ghaction-github-pages](https://github.com/crazy-max/ghaction-github-pages) from 2 to 4.
- [Release notes](https://github.com/crazy-max/ghaction-github-pages/releases)
- [Commits](crazy-max/ghaction-github-pages@v2...v4)

---
updated-dependencies:
- dependency-name: crazy-max/ghaction-github-pages
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/ci.yml

@@ -121,7 +121,7 @@ jobs:
           github.event_name == 'push' && github.ref == 'refs/heads/master' &&
           matrix.target.os == 'linux' && matrix.target.cpu == 'amd64' &&
           matrix.branch == 'devel'
-        uses: crazy-max/ghaction-github-pages@v2
+        uses: crazy-max/ghaction-github-pages@v4
         with:
           build_dir: fusion/htmldocs
           target_branch: gh-pages