mark autoroller flaky (#129745)

Unblock tree while I investigate: https://github.com/flutter/flutter/issues/129744
diff --git a/.ci.yaml b/.ci.yaml
index c62d804..e5ebac4 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -243,6 +243,8 @@
 
   - name: Linux packages_autoroller
     presubmit: false
+    # TODO(fujino): https://github.com/flutter/flutter/issues/129744
+    bringup: true
     recipe: pub_autoroller/pub_autoroller
     timeout: 30
     enabled_branches: