Marks Windows module_test to be unflaky (#134121)

<!-- meta-tags: To be used by the automation script only, DO NOT MODIFY.
{
  "name": "Windows module_test"
}
-->
The issue flutter/flutter#133639 has been closed, and 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:%22Windows%20module_test%22).
This test can be marked as unflaky.

.ci.yaml

@@ -4712,7 +4712,6 @@ targets:
       - .ci.yaml
 
   - name: Windows module_test
-    bringup: true # Flaky https://github.com/flutter/flutter/issues/133639
     recipe: devicelab/devicelab_drone
     timeout: 60
     properties: