Marks Windows module_custom_host_app_name_test to be flaky (flutter#134645)

<!-- meta-tags: To be used by the automation script only, DO NOT MODIFY.
{
  "name": "Windows module_custom_host_app_name_test"
}
-->
Issue link: flutter#134644

Author: fluttergithubbot

.ci.yaml

@@ -4599,6 +4599,7 @@ targets:
       task_name: hot_mode_dev_cycle_win_target__benchmark
 
   - name: Windows module_custom_host_app_name_test
+    bringup: true # Flaky https://github.com/flutter/flutter/issues/134644
     recipe: devicelab/devicelab_drone
     timeout: 60
     properties: