add dimenstion for arm packaging (#122770) (#123037)

Add dimenstion for arm packaging
diff --git a/.ci.yaml b/.ci.yaml
index 1fa7679..188daa5 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -4954,6 +4954,8 @@
       task_name: flutter_packaging
       tags: >
         ["framework", "hostonly", "shard", "mac"]
+    dimensions:
+      cpu: "arm64"
 
   - name: Windows flutter_packaging
     recipe: packaging/packaging