Fix typo

app/mailers/custom_mailer.rb

@@ -11,7 +11,7 @@
 #
 # Send email via Sidekiq:
 #
-#     CustomMailer.with(user: u, subject: "Important announcement", body: body).custom_message.deliver_later
+#     CustomMailer.with(user: user, subject: "Important announcement", body: body).custom_message.deliver_later
 #
 class CustomMailer < ApplicationMailer
   def custom_message