mark linux packages_autoroller flaky because of token issue (flutter#131970)

unblock tree from flutter#131968

Author: christopherfujino

.ci.yaml

@@ -245,6 +245,7 @@ targets:
     presubmit: false
     recipe: pub_autoroller/pub_autoroller
     timeout: 30
+    bringup: true # https://github.com/flutter/flutter/issues/131968
     enabled_branches:
       # Don't run this on release branches
       - master