remove redundant method

app/mailers/resend_invitation_mailer.rb

@@ -1,6 +1,4 @@
 class ResendInvitationMailer < NotifyMailer
-  include Rails.application.routes.url_helpers
-
   def resend_invitation_email(user)
     user.send_confirmation_instructions
   end

app/models/user.rb

@@ -174,10 +174,6 @@ class User < ApplicationRecord
     super && active?
   end
 
-  def resend_invitation_email
-    ResendInvitationMailer.resend_invitation_email(self).deliver_later
-  end
-
 protected
 
   # Checks whether a password is needed or not. For validations only.