Marks Mac flutter_gallery_macos__start_up to be unflaky (#112088)

diff --git a/.ci.yaml b/.ci.yaml
index 0686774..de760cc 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -2505,7 +2505,6 @@
       task_name: flutter_gallery_macos__compile
 
   - name: Mac flutter_gallery_macos__start_up
-    bringup: true # New target https://github.com/flutter/flutter/issues/109633
     presubmit: false
     recipe: devicelab/devicelab_drone
     timeout: 60