Marks Linux firebase_oriol33_abstract_method_smoke_test to be unflaky (#128398)

<!-- meta-tags: To be used by the automation script only, DO NOT MODIFY.
{
  "name": "Linux firebase_oriol33_abstract_method_smoke_test"
}
-->
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%20firebase_oriol33_abstract_method_smoke_test%22).
This test can be marked as unflaky.

.ci.yaml

@@ -414,7 +414,6 @@ targets:
       - .ci.yaml
 
   - name: Linux firebase_oriol33_abstract_method_smoke_test
-    bringup: true
     recipe: firebaselab/firebaselab
     timeout: 60
     properties: