Update Android iOS test script after https://github.com/flutter/engine/pull/18660

Change-Id: I357b6335ead237d51559d1da280f5c7fa5dc93b0
Reviewed-on: https://flutter-review.googlesource.com/c/recipes/+/3160
Reviewed-by: Godofredo Contreras <godofredoc@google.com>