Update actions/upload-artifact to @v4

Author: adamgraham

.github/workflows/unity-package.yml

@@ -85,7 +85,7 @@ jobs:
           NPM_TOKEN: ${{ secrets.token }}
 
       - name: Upload artifact
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: docs
           path: docs~/public