Mark flutter_gallery_sksl_warmup__transition_perf_e2e as flaky (#83300)

diff --git a/.ci.yaml b/.ci.yaml
index 0d16e9b..7afe64e 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -889,6 +889,7 @@
 
   - name: linux_flutter_gallery_sksl_warmup__transition_perf_e2e
     builder: Linux flutter_gallery_sksl_warmup__transition_perf_e2e
+    bringup: true
     presubmit: false
     scheduler: luci