rmeoved unnecessary code from Queue ES6 code

Author: loiane

chapter04/01-Queue2.js

@@ -11,13 +11,11 @@ let Queue2 = (function () {
         enqueue(element) {
             let q = items.get(this);
             q.push(element);
-            items.set(this, q)
         }
 
         dequeue() {
             let q = items.get(this);
             let r = q.shift();
-            items.set(this, q);
             return r;
         }
 

chapter04/02-UsingQueues.js

@@ -1,4 +1,4 @@
-let queue = new Queue();
+let queue = new Queue2();
 console.log(queue.isEmpty()); //outputs true
 queue.enqueue("John");
 queue.enqueue("Jack");