Fix: Use matching upload-artifact version

We updated the download-artifact version in #235

Author: phil-opp

.github/workflows/build-site.yml

@@ -26,7 +26,7 @@ jobs:
         run: ./zola build
 
       - name: Upload Generated Site
-        uses: actions/upload-artifact@v2
+        uses: actions/upload-artifact@v4
         with:
           name: generated_site
           path: public