Fix #2251: Refine phrasing for "allowed to start" (#2308)

* Fix #2251: Refine phrasing for "allowed to start"

The phrasing using "delay" is confusing.  Replace it with "disallow"
which reflects more precisely what happens.  When a context is not
allowed to start, it isn't really "delayed"; it can only start under
specific actions with a user-gesture.

* Clean up phrasing a bit

Co-authored-by: Raymond Toy <rtoy@chromium.org>

index.bs

@@ -1372,8 +1372,8 @@ interface AudioContext : BaseAudioContext {
 
 An {{AudioContext}} is said to be <dfn>allowed to start</dfn> if the user agent
 allows the context state to transition from "{{AudioContextState/suspended}}" to
-"{{AudioContextState/running}}". A user agent may delay this initial transition,
-to allow it only when the {{AudioContext}}'s [=relevant global object=] has
+"{{AudioContextState/running}}". A user agent may disallow this initial transition,
+and to allow it only when the {{AudioContext}}'s [=relevant global object=] has
 [=sticky activation=].
 
 {{AudioContext}} has an internal slot: