the AC passed to CreateIteratorFromClosure should return completions

Author: michaelficarra

spec.emu

@@ -24,7 +24,7 @@ copyright: false
         1. If _value_ is ~done~, then
           1. If _buffer_ is not empty, then
             1. Perform Completion(Yield(CreateArrayFromList(_buffer_))).
-          1. Return ~unused~.
+          1. Return NormalCompletion(~unused~).
         1. Append _value_ to _buffer_.
         1. If the number of elements in _buffer_ is ℝ(_chunkSize_), then
           1. Let _completion_ be Completion(Yield(CreateArrayFromList(_buffer_))).
@@ -48,7 +48,7 @@ copyright: false
       1. Let _buffer_ be a new empty List.
       1. Repeat,
         1. Let _value_ be ? IteratorStepValue(_iterated_).
-        1. If _value_ is ~done~, return ~unused~.
+        1. If _value_ is ~done~, return NormalCompletion(~unused~).
         1. Append _value_ to _buffer_.
         1. If the number of elements in _buffer_ is ℝ(_windowSize_), then
           1. Let _completion_ be Completion(Yield(CreateArrayFromList(_buffer_))).