fix failing tests for merge_request_widget_spec.js

app/assets/javascripts/merge_request_widget.js.es6

@@ -4,6 +4,8 @@
 /* global merge_request_widget */
 /* global Turbolinks */
 
+require('./smart_interval');
+
 ((global) => {
   var indexOf = [].indexOf || function(item) { for (var i = 0, l = this.length; i < l; i++) { if (i in this && this[i] === item) return i; } return -1; };