Mark hello_world_macos__compile unflaky (flutter#160998)

This should have been marked unflaky when
flutter#159542 was closed.

Author: jmagman

.ci.yaml

@@ -4201,7 +4201,6 @@ targets:
       - DEPS
 
   - name: Mac_benchmark hello_world_macos__compile
-    bringup: true # Flaky https://github.com/flutter/flutter/issues/159542
     presubmit: false
     recipe: devicelab/devicelab_drone
     timeout: 60