Update Response DSL comment
to properly reflect the latest implementation behavior.
@@ -16,10 +16,11 @@ import (
// success response is associated with a different tag value). gRPC responses
// may only define one success response.
//
-// Response may appear in an API or service expression to define error responses
-// common to all the API or service methods. Response may also appear in a
-// method expression to define both success and error responses specific to the
-// method.
+// Response may appear in a service expression to define error responses common
+// to all the service methods. Response may also appear in a method expression
+// to define both success and error responses specific to the method. In both
+// cases Response must appear in the transport specific DSL (i.e. in a HTTP or
+// gRPC subexpression).
//
// Response accepts one to three arguments. Success response accepts a status
// code as first argument. If the first argument is a status code then a
