Fix error when sending moderation notification (#13014)

Since the statuses helper is not loaded, the rtl helper cannot be found
and the email cannot be sent.

app/mailers/user_mailer.rb

@@ -6,6 +6,7 @@ class UserMailer < Devise::Mailer
   helper :accounts
   helper :application
   helper :instance
+  helper :statuses
 
   add_template_helper RoutingHelper