Remove unused variable from mailer

The second variable passed by Devise is actually a hash, not a token.

app/mailers/spree/user_mailer_decorator.rb

@@ -5,9 +5,10 @@ Spree::UserMailer.class_eval do
          :subject => t(:welcome_to) + Spree::Config[:site_name])
   end
 
-  def confirmation_instructions(user, token)
+  # Overriding `Spree::UserMailer.confirmation_instructions` which is
+  # overriding `Devise::Mailer.confirmation_instructions`.
+  def confirmation_instructions(user, _opts)
     @user = user
-    @token = token
     subject = t('spree.user_mailer.confirmation_instructions.subject')
     mail(to: user.email,
          from: from_address,