Reword to avoid introducing 'subscription stream' term

Author: benjie

spec/Section 6 -- Execution.md

@@ -236,9 +236,9 @@ connectivity.
 **Delivery Agnostic**
 
 GraphQL subscriptions do not require any specific serialization format or
-transport mechanism. GraphQL specifies algorithms for the creation of a
-subscription stream, the content of each payload on that stream, and the closing
-of that stream. There are intentionally no specifications for message
+transport mechanism. GraphQL specifies algorithms for the creation of the
+response stream, the content of each payload on that stream, and the closing of
+that stream. There are intentionally no specifications for message
 acknowledgement, buffering, resend requests, or any other quality of service
 (QoS) details. Message serialization, transport mechanisms, and quality of
 service details should be chosen by the implementing service.