Turn the packages roller bot back on (flutter#155842)

Turns the roller bot back on, as it should have been fixed by flutter#155794.

Author: gmackall

.ci.yaml

@@ -388,7 +388,6 @@ targets:
 
   - name: Linux packages_autoroller
     presubmit: false
-    bringup: true # https://github.com/flutter/flutter/issues/155704
     recipe: pub_autoroller/pub_autoroller
     # This takes a while because we need to fetch network dependencies and run
     # Gradle for every android app in the repo