spec: Fix typo (#13)

Fix `syncItems` → `asyncItems` in algorithm.

Author: ljharb

spec.html

@@ -59,7 +59,7 @@ <h1><ins>Array.fromAsync ( _asyncItems_ [ , _mapfn_ [ , _thisArg_ ] ] )</ins></h
             1. If _usingAsyncIterator_ is not *undefined*, then
               1. Let _iteratorRecord_ be ? GetIterator(_asyncItems_, ~async~, _usingAsyncIterator_).
             1. Else,
-              1. Let _iteratorRecord_ be ? CreateAsyncFromSyncIterator(GetIterator(_syncItems_, ~sync~, _usingSyncIterator_)).
+              1. Let _iteratorRecord_ be ? CreateAsyncFromSyncIterator(GetIterator(_asyncItems_, ~sync~, _usingSyncIterator_)).
             1. Let _k_ be 0.
             1. Repeat,
               1. If _k_ &ge; 2<sup>53</sup> - 1, then