Reverts "Promote fuchsia build v2 to prod." (flutter/engine#47779)

Reverts flutter/engine#47729
Initiated by: bdero
This change reverts the following previous change:
Original Description:
The current failure in staging is because the service account does not have write access to the release bucket.

[C++, Objective-C, Java style guides]: https://github.com/flutter/engine/blob/main/CONTRIBUTING.md#style

engine/src/flutter/.ci.yaml

@@ -159,7 +159,6 @@ targets:
     timeout: 60
 
   - name: Linux Fuchsia
-    bringup: true
     recipe: engine/engine
     properties:
       build_fuchsia: "true"
@@ -217,6 +216,7 @@ targets:
       - web_sdk/**
 
   - name: Linux linux_fuchsia
+    bringup: true
     recipe: engine_v2/engine_v2
     timeout: 60
     properties: