Linux docs_test is 1.99% flaky

[flutter-dashboard]

The post-submit test builder Linux docs_test had a flaky ratio 1.99% for the past 15 days, which is the flakist test below 200.00% threshold.

One recent flaky example for a same commit: *
Commit:
Failed build:
Succeeded build:

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).