Revert "Remove out of date require"

This reverts commit ffc0d0e8bf.

assets/javascripts/wizard-custom.js

@@ -44,6 +44,8 @@
 
 //= require discourse/app/adapters/rest
 
+//= require message-bus
+
 //= require discourse/app/models/login-method
 //= require discourse/app/models/permission-type
 //= require discourse/app/models/archetype