Fixes event listener context

This is intead of re-initializing the mini-pipeline graph after the vue app is mounted

app/assets/javascripts/merge_request_widget/widget_bundle.js.es6

@@ -12,9 +12,5 @@ $(() => {
   gl.MergeRequestWidgetApp = new Vue({
     el: rootEl,
     data: widgetSharedStore.data,
-    mounted() {
-      // re-init the MiniPipelineGraph because of Vue is messing with the element
-      merge_request_widget.initMiniPipelineGraph();
-    },
   });
 });

app/assets/javascripts/mini_pipeline_graph_dropdown.js.es6

@@ -28,7 +28,7 @@
      * All dropdown events are fired at the .dropdown-menu's parent element.
      */
     bindEvents() {
-      $(this.container).on('shown.bs.dropdown', this.getBuildsList);
+      $(document).on('shown.bs.dropdown', this.container, this.getBuildsList);
     }
 
     /**