remove unnecessary variable to return directly

Author: mmyeon

contains-duplicate/mmyeon.js

@@ -18,7 +18,5 @@
  */
 
 var containsDuplicate = function (nums) {
-  const uniqueNumbers = new Set(nums);
-
-  return uniqueNumbers.size !== nums.length;
+  return new Set(nums).size !== nums.length;
 };