Marks Mac_android microbenchmarks to be flaky (#118693)

Author: fluttergithubbot

.ci.yaml

@@ -3345,6 +3345,7 @@ targets:
       task_name: integration_ui_frame_number
 
   - name: Mac_android microbenchmarks
+    bringup: true # Flaky https://github.com/flutter/flutter/issues/118692
     recipe: devicelab/devicelab_drone
     presubmit: false
     timeout: 60