clarify documentation for makeArray

Resolve #14741.

packages/ember-utils/lib/make-array.js

@@ -5,7 +5,7 @@ const { isArray } = Array;
 /**
  Forces the passed object to be part of an array. If the object is already
  an array, it will return the object. Otherwise, it will add the object to
- an array. If obj is `null` or `undefined`, it will return an empty array.
+ an array. If object is `null` or `undefined`, it will return an empty array.
 
  ```javascript
  import { makeArray } from '@ember/array';
@@ -17,9 +17,9 @@ const { isArray } = Array;
  makeArray('lindsay');   // ['lindsay']
  makeArray([1, 2, 42]);  // [1, 2, 42]
 
- let controller = ArrayProxy.create({ content: [] });
+ let proxy = ArrayProxy.create({ content: [] });
 
- makeArray(controller) === controller;  // true
+ makeArray(proxy) === proxy;  // false
  ```
 
  @method makeArray