Mark firebase_release_smoke_test unflaky (#161006)

`firebase_release_smoke_test` was [marked
flaky](flutter/flutter#147338) due to a firebase
outage in April.
`firebase_android_embedding_v2_smoke_test` was deleted with
flutter/flutter#158223.
`firebase_abstract_method_smoke_test` was deleted with #159145

Closes flutter/flutter#147335.

Author: jmagman

.ci.yaml

@@ -647,7 +647,6 @@ targets:
 
   - name: Linux firebase_release_smoke_test
     recipe: firebaselab/firebaselab
-    bringup: true # https://github.com/flutter/flutter/issues/147335
     timeout: 60
     properties:
       dependencies: >-