follow up on issue #68: restoring Fulfill entry.[[Instantiate]] with instance, it was removed in 85318ae (shame on me)

Author: caridy

index.bs

@@ -625,6 +625,7 @@ Registry instances are initially created with the internal slots described in th
 1. Let _instance_ be Instantiation(_loader_, _optionalInstance_, _source_).
 1. ReturnIfAbrupt(_instance_).
 1. // TODO: edge case: what if _instance_ is a thenable function?
+1. Fulfill _entry_.[[Instantiate]] with _instance_.
 1. Let _deps_ be a new empty List.
 1. If _instance_ is a Module Record, then:
   1. Assert: _instance_ is a Source Text Module Record.