Use autocomplete paths from data attr

app/assets/javascripts/protected_tags/protected_tag_access_dropdown.js

@@ -17,8 +17,8 @@ export default class ProtectedTagAccessDropdown {
     this.accessLevelsData = accessLevelsData.roles;
     this.$dropdown = $dropdown;
     this.$wrap = this.$dropdown.closest(`.${this.accessLevel}-container`);
-    this.usersPath = '/autocomplete/users.json';
-    this.groupsPath = '/autocomplete/project_groups.json';
+    this.usersPath = $('.js-protected-tags-container').data('users-autocomplete');
+    this.groupsPath = $('.js-protected-tags-container').data('groups-autocomplete');
     this.defaultLabel = this.$dropdown.data('defaultLabel');
 
     this.setSelectedItems([]);

app/views/projects/protected_tags/_index.html.haml

 - content_for :page_specific_javascripts do
   = page_specific_javascript_bundle_tag('protected_tags')
 
-.row.prepend-top-default.append-bottom-default
+.row.prepend-top-default.append-bottom-default.js-protected-tags-container{ data: { "groups-autocomplete" => "#{autocomplete_project_groups_path(format: :json)}", "users-autocomplete" => "#{autocomplete_users_path(format: :json)}" } }
   .col-lg-3
     %h4.prepend-top-0
       Protected Tags