Marks Mac_ios dynamic_path_stroke_tessellation_perf_ios__timeline_summary to be unflaky (#167261)

<!-- meta-tags: To be used by the automation script only, DO NOT MODIFY.
{
"name": "Mac_ios
dynamic_path_stroke_tessellation_perf_ios__timeline_summary"
}
-->
The test has been passing for [50 consecutive
runs](https://data.corp.google.com/sites/flutter_infra_metrics_datasite/flutter_check_test_flakiness_status_dashboard/?p=BUILDER_NAME:%22Mac_ios%20dynamic_path_stroke_tessellation_perf_ios__timeline_summary%22).
This test can be marked as unflaky.

.ci.yaml

diff --git a/.ci.yaml b/.ci.yaml
index af6d78c..932f6af 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -3667,7 +3667,6 @@
   - name: Mac_ios dynamic_path_stroke_tessellation_perf_ios__timeline_summary
     recipe: devicelab/devicelab_drone
     presubmit: false
-    bringup: true
     timeout: 60
     properties:
       tags: >