Fix Iterator prototype reference

Follows tc39/ecma262#3395.

index.bs

@@ -12528,7 +12528,7 @@ prototype for [=default iterator objects=]
 for the interface.
 
 The \[[Prototype]] [=/internal slot=] of an [=iterator prototype object=]
-must be {{%IteratorPrototype%}}.
+must be {{%Iterator.prototype%}}.
 
 <div algorithm>
   The <dfn>iterator result</dfn> for a [=value pair=] |pair| and a kind |kind| is given by the