[runtime] We don't need an actual instance type for JSIteratorResult.

src/factory.h

Index: src/factory.h
diff --git a/src/factory.h b/src/factory.h
index da3e89d8442ea5e71bd597ee4e26ccf2baaa1ac9..70653f5943367efebe3ea5003b029bbec200406f 100644
--- a/src/factory.h
+++ b/src/factory.h
@@ -469,11 +469,6 @@ class Factory final {
   Handle<JSMapIterator> NewJSMapIterator();
   Handle<JSSetIterator> NewJSSetIterator();
 
-  // Creates a new JSIteratorResult object with the arguments {value} and
-  // {done}.  Implemented according to ES6 section 7.4.7 CreateIterResultObject.
-  Handle<JSIteratorResult> NewJSIteratorResult(Handle<Object> value,
-                                               Handle<Object> done);
-
   // Allocates a bound function.
   MaybeHandle<JSBoundFunction> NewJSBoundFunction(
       Handle<JSReceiver> target_function, Handle<Object> bound_this,