Expose AbortSignal.timeout on all globals

Delete the Exposed attribute from AbortSignal.timeout, letting it
inherit [Exposed=*] from AbortSignal.

Cf. whatwg/html#9893 where other timers are
being exposed in ShadowRealm global contexts.

dom.bs

@@ -1847,7 +1847,7 @@ to <a for=AbortController>signal abort</a> on <a>this</a> with <var>reason</var>
 [Exposed=*]
 interface AbortSignal : EventTarget {
   [NewObject] static AbortSignal abort(optional any reason);
-  [Exposed=(Window,Worker), NewObject] static AbortSignal timeout([EnforceRange] unsigned long long milliseconds);
+  [NewObject] static AbortSignal timeout([EnforceRange] unsigned long long milliseconds);
   [NewObject] static AbortSignal _any(sequence&lt;AbortSignal> signals);
 
   readonly attribute boolean aborted;