Marks Mac_ios flutter_view_ios__start_up to be unflaky (#102224)

* Marks Mac_ios flutter_view_ios__start_up to be unflaky

* update mode
Co-authored-by: Keyong Han <keyonghan@google.com>

.ci.yaml

@@ -3358,7 +3358,6 @@ targets:
     scheduler: luci
 
   - name: Mac_ios flutter_view_ios__start_up
-    bringup: true # Flaky https://github.com/flutter/flutter/issues/98419
     recipe: devicelab/devicelab_drone
     presubmit: false
     timeout: 60