Mac framework_tests_widgets is 2.02% flaky

[flutterflakybot]

The post-submit test builder Mac framework_tests_widgets had a flaky ratio 2.02% for the past 15 days, which is above our 2.00% threshold.

One recent flaky example for a same commit: https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20framework_tests_widgets/1331
Commit: flutter@d6f4bea
Failed build:
https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20framework_tests_widgets/1331
https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20framework_tests_widgets/1320
https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20framework_tests_widgets/1319
https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20framework_tests_widgets/1310
https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20framework_tests_widgets/1308
Succeeded build (3 most recent):
https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20framework_tests_widgets/1509
https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20framework_tests_widgets/1508
https://ci.chromium.org/ui/p/flutter/builders/prod/Mac%20framework_tests_widgets/1507

Please follow https://github.com/flutter/flutter/wiki/Reducing-Test-Flakiness#fixing-flaky-tests to fix the flakiness and enable the test back after validating the fix (internal dashboard to validate: go/flutter_test_flakiness).