Update window.dart

lib/web_ui/lib/src/engine/window.dart

@@ -222,6 +222,7 @@ typedef _JsSetUrlStrategy = void Function(JsUrlStrategy?);
 //
 // TODO: Add integration test https://github.com/flutter/flutter/issues/66852
 @JS('_flutter_web_set_location_strategy')
+// ignore: unused_element
 external set _jsSetUrlStrategy(_JsSetUrlStrategy? newJsSetUrlStrategy);
 
 UrlStrategy? _createDefaultUrlStrategy() {