Marks Linux_pixel_7pro integration_ui_keyboard_resize to be unflaky (#143440)

<!-- meta-tags: To be used by the automation script only, DO NOT MODIFY.
{
  "name": "Linux_pixel_7pro integration_ui_keyboard_resize"
}
-->
The issue https://github.com/flutter/flutter/issues/140645 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:%22Linux_pixel_7pro%20integration_ui_keyboard_resize%22).
This test can be marked as unflaky.

.ci.yaml

@@ -2484,7 +2484,6 @@ targets:
       task_name: integration_ui_driver
 
   - name: Linux_pixel_7pro integration_ui_keyboard_resize
-    bringup: true # Flaky https://github.com/flutter/flutter/issues/140645
     recipe: devicelab/devicelab_drone
     presubmit: false
     timeout: 60