Mark integration_ui_test_test_macos unflaky (#160999)

This should have been marked unflaky when
https://github.com/flutter/flutter/issues/152212 was closed.

.ci.yaml

diff --git a/.ci.yaml b/.ci.yaml
index aef633c..9c993e8 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -4210,7 +4210,6 @@
       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