Retry plugin_test_ios in presubmit (flutter#151773)

For flutter#151772

This test is flaking frequently in presubmit and blocking engine -> framework rolls as in flutter#151762 that only contained a Skia roll.

Author: zanderso

.ci.yaml

@@ -3979,6 +3979,9 @@ targets:
       tags: >
         ["devicelab", "hostonly", "mac"]
       task_name: plugin_test_ios
+      # Retry for flakes caused by https://github.com/flutter/flutter/issues/151772
+      presubmit_max_attempts: "2"
+      test_timeout_secs: "3600"
     runIf:
       - dev/**
       - packages/flutter_tools/**