Merge branch '12364-sortable-default-mixin' into 'master'

Removes EE differences for sortable_default_options

Closes gitlab-ee#12364

See merge request gitlab-org/gitlab-ce!30074

app/assets/javascripts/boards/mixins/sortable_default_options.js

 /* global DocumentTouch */
 
 import $ from 'jquery';
-import sortableConfig from '../../sortable/sortable_config';
+import sortableConfig from 'ee_else_ce/sortable/sortable_config';
 
 export function sortableStart() {
   $('.has-tooltip')