Update the timeout to 3h for mac build in staging. (#41048)

Update the timeout to 3h for mac build in staging.

.ci.yaml

diff --git a/.ci.yaml b/.ci.yaml
index 0822678..1e57672 100644
--- a/.ci.yaml
+++ b/.ci.yaml
@@ -368,6 +368,7 @@
     properties:
       config_name: mac_unopt
       add_recipes_cq: "true"
+    timeout: 180  # set timeout to 3H while this runs on staging.
 
   - name: Mac Unopt
     recipe: engine/engine_unopt