Update Sortable package path

app/assets/javascripts/boards/components/board.js

 /* eslint-disable comma-dangle, space-before-function-paren, one-var */
 import $ from 'jquery';
-import Sortable from 'vendor/Sortable';
+import Sortable from 'sortablejs';
 import Vue from 'vue';
 import AccessorUtilities from '../../lib/utils/accessor';
 import boardList from './board_list.vue';

app/assets/javascripts/boards/components/board_list.vue

 <script>
-import Sortable from 'vendor/Sortable';
+import Sortable from 'sortablejs';
 import boardNewIssue from './board_new_issue.vue';
 import boardCard from './board_card.vue';
 import eventHub from '../eventhub';

app/assets/javascripts/label_manager.js

 /* eslint-disable comma-dangle, class-methods-use-this, no-underscore-dangle, no-param-reassign, no-unused-vars, consistent-return, func-names, space-before-function-paren, max-len */
 import $ from 'jquery';
-import Sortable from 'vendor/Sortable';
+import Sortable from 'sortablejs';
 import flash from './flash';
 import axios from './lib/utils/axios_utils';

spec/javascripts/boards/board_list_spec.js

@@ -3,7 +3,7 @@
 import Vue from 'vue';
 import MockAdapter from 'axios-mock-adapter';
 import axios from '~/lib/utils/axios_utils';
-import Sortable from 'vendor/Sortable';
+import Sortable from 'sortablejs';
 import BoardList from '~/boards/components/board_list.vue';
 import eventHub from '~/boards/eventhub';
 import '~/boards/mixins/sortable_default_options';