update 'final code' to be same as previous code

Author: mansona

guides/v3.1.0/tutorial/simple-component.md

@@ -384,7 +384,7 @@ module('Integration | Component | rental listing', function (hooks) {
     await click('.image');
     assert.ok(this.element.querySelector('.image.wide'), 'rendered wide after click');
     await click('.image');
-    assert.notOk(this.$('.image.wide'), 'rendered small after second click');
+    assert.notOk(this.element.querySelector('.image.wide'), 'rendered small after second click');
   });
 });
 ```