Change import from helpers/jquery to jquery

**Why?**
- Importing the helper module adds a layer of indirection
- It's more consistent and expected to see us just import
  the regular ol' jquery

spec/frontend/notes/components/notes_app_spec.js

-import $ from 'helpers/jquery';
+import $ from 'jquery';
 import AxiosMockAdapter from 'axios-mock-adapter';
 import Vue from 'vue';
 import { mount } from '@vue/test-utils';