Temporarily disable the mac/android test on LUCI. (#64729)

Because the test bed's CPU is too hot.

Bug: https://github.com/flutter/flutter/issues/64723

dev/devicelab/manifest.yaml

@@ -259,7 +259,6 @@ tasks:
       Checks that flavored builds work on Android.
     stage: devicelab
     required_agent_capabilities: ["mac/android"]
-    on_luci: true
 
   channels_integration_test:
     description: >