upgrade to Ember 3.13

package.json

@@ -45,7 +45,7 @@
     "ember-qunit": "^4.1.2",
     "ember-resolver": "^5.0.1",
     "ember-sinon": "^3.0.0",
-    "ember-source": "~3.5.0",
+    "ember-source": "~3.13.3",
     "ember-source-channel-url": "^1.1.0",
     "ember-try": "^1.0.0",
     "eslint-plugin-ember": "^5.2.0",

tests/unit/helpers/chunk-test.js

@@ -1,6 +1,3 @@
-import emberArrayProxy from '@ember/array/proxy';
-import { A as emberArray } from '@ember/array';
-import { computed } from '@ember/object';
 import { chunk } from 'dummy/helpers/chunk';
 import { module, test } from 'qunit';
 
@@ -56,17 +53,4 @@ module('Unit | Helper | chunk', function() {
     assert.deepEqual(result1, expectedResult1, 'should return array of chunked arrays');
     assert.deepEqual(result2, expectedResult2, 'should return array of chunked arrays');
   });
-
-  test('it handles arrays with computed property lengths', function(assert) {
-    let ap = emberArrayProxy.extend({
-      content: emberArray([1, 2, 3]),
-      length: computed('content.[]', function() {
-        return this.get('content.length');
-      })
-    }).create();
-
-    let expectedResult = [[1], [2], [3]];
-    let result = chunk(1, ap);
-    assert.deepEqual(result, expectedResult, 'should return array of chunked arrays');
-  });
 });