Mark module_test_ios tests unflaky (#125498)

[Dart workaround](https://dart-review.googlesource.com/c/sdk/+/297821 ) to prevent the flake has rolled into the framework.  Mark the tests unflaky so we can detect if it happens again when a fix for the underlying issue lands.

https://github.com/flutter/flutter/issues/125425#issuecomment-1522142360

Reverts https://github.com/flutter/flutter/pull/125426

.ci.yaml

@@ -2942,7 +2942,6 @@ targets:
 
   - name: Mac module_test_ios
     recipe: devicelab/devicelab_drone
-    bringup: true # Flaky: https://github.com/flutter/flutter/issues/125425
     timeout: 60
     properties:
       cpu: x86 # Codesigning fails on ARM https://github.com/flutter/flutter/issues/112033
@@ -2962,7 +2961,6 @@ targets:
 
   - name: Mac_arm64_ios module_test_ios
     recipe: devicelab/devicelab_drone
-    bringup: true # Flaky: https://github.com/flutter/flutter/issues/125425
     presubmit: false
     timeout: 60
     properties: