(actions) bump upload-pages-artifact to v4 (#1070)

Author: MatthijsBurgh

.github/workflows/docs.yml

@@ -24,7 +24,7 @@ jobs:
         run: npm run doc
       - name: Upload static files as artifact
         id: deployment
-        uses: actions/upload-pages-artifact@v3
+        uses: actions/upload-pages-artifact@v4
         with:
           path: docs/