Update actions/upload-pages-artifact action to v4 (#245)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/jekyll-gh-pages.yml

@@ -35,7 +35,7 @@ jobs:
           source: ./
           destination: ./_site
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v3
+        uses: actions/upload-pages-artifact@v4
 
   # Deployment job
   deploy: