Marks Mac_android hot_mode_dev_cycle__benchmark to be flaky (#138073)

<!-- meta-tags: To be used by the automation script only, DO NOT MODIFY.
{
  "name": "Mac_android hot_mode_dev_cycle__benchmark"
}
-->
Issue link: https://github.com/flutter/flutter/issues/138072

.ci.yaml

@@ -3728,6 +3728,7 @@ targets:
       task_name: hello_world_android__compile
 
   - name: Mac_android hot_mode_dev_cycle__benchmark
+    bringup: true # Flaky https://github.com/flutter/flutter/issues/138072
     recipe: devicelab/devicelab_drone
     presubmit: false
     timeout: 60