Bump actions/upload-pages-artifact from 3 to 4

Bumps [actions/upload-pages-artifact](https://github.com/actions/upload-pages-artifact) from 3 to 4.
- [Release notes](https://github.com/actions/upload-pages-artifact/releases)
- [Commits](actions/upload-pages-artifact@v3...v4)

---
updated-dependencies:
- dependency-name: actions/upload-pages-artifact
  dependency-version: '4'
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

.github/workflows/pages.yml

@@ -43,7 +43,7 @@ jobs:
           WEBSITE_LANGUAGE=es sphinx-build unconference unconference/_build/es -b html
           cp index.html unconference/_build/
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v3
+        uses: actions/upload-pages-artifact@v4
         with:
           path: 'unconference/_build'
       - name: Deploy to GitHub Pages