Change CAPTCHA handling to be only on email verification

This simplifies the implementation considerably, and while not providing
ideal UX, it's the most flexible approach.

app/controllers/auth/confirmations_controller.rb

@@ -22,8 +22,6 @@ class Auth::ConfirmationsController < Devise::ConfirmationsController
   end
 
   def show
-    clear_captcha!
-
     old_session_values = session.to_hash
     reset_session
     session.update old_session_values.except('session_id')
@@ -63,10 +61,6 @@ class Auth::ConfirmationsController < Devise::ConfirmationsController
     invite.present? && !invite.max_uses.nil?
   end
 
-  def captcha_context
-    'email-confirmation'
-  end
-
   def set_pack
     use_pack 'auth'
   end