fix: close for 'Unsaved Changes' modal, #9284 (#9313)

Missing reference to the controller instance.

public/app/features/dashboard/unsaved_changes_modal.ts

@@ -10,7 +10,7 @@ const  template = `
       <span class="p-l-1">Unsaved changes</span>
     </h2>
 
-    <a class="modal-header-close" ng-click="dismiss();">
+    <a class="modal-header-close" ng-click="ctrl.dismiss();">
       <i class="fa fa-remove"></i>
     </a>
   </div>