ci: 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/publish.yml

@@ -35,7 +35,7 @@ jobs:
           python-version: 3.12
       - run: pip install uv
       - run: uv run mkdocs build
-      - uses: actions/upload-pages-artifact@v3
+      - uses: actions/upload-pages-artifact@v4
         if: github.ref == 'refs/heads/main'
         with:
           path: site