Marks Mac integration_ui_test_test_macos to be flaky (#152213)

<!-- meta-tags: To be used by the automation script only, DO NOT MODIFY.
{
  "name": "Mac integration_ui_test_test_macos"
}
-->
Issue link: flutter/flutter#152212

Author: fluttergithubbot

.ci.yaml

@@ -3876,6 +3876,7 @@ targets:
       task_name: hello_world_macos__compile
 
   - name: Mac integration_ui_test_test_macos
+    bringup: true # Flaky https://github.com/flutter/flutter/issues/152212
     recipe: devicelab/devicelab_drone
     presubmit: false
     timeout: 60