Update build.yml

Author: nahtheol

.github/workflows/build.yml

@@ -26,7 +26,7 @@ jobs:
         run: flutter build ipa --release -t lib/main_prod.dart
 
       - name: Upload artifact
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: app-ipa
           path: build/ios/ipa