Marks Mac_arm64 tool_host_cross_arch_tests to be unflaky (#112558)

diff --git a/.ci.yaml b/.ci.yaml
index c91c0d1..f639f43 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -2867,7 +2867,6 @@
       - .ci.yaml
 
   - name: Mac_arm64 tool_host_cross_arch_tests
-    bringup: true # Mac_arm64 variant https://github.com/flutter/flutter/pull/109889
     recipe: flutter/flutter_drone
     timeout: 60
     properties: