[Rails5] Add `raise: false` to skip_before_action in authenticates_with_two_factor.rb

Rails 5.0 raises `ArgumentErrror` if an unrecognised callback is skipped.
https://github.com/rails/rails/commit/8b88df94ebda2e829782f514ff51caeaf5e694dd
This commit adds `raise: false` to the filter.

app/controllers/concerns/authenticates_with_two_factor.rb

@@ -10,7 +10,7 @@ module AuthenticatesWithTwoFactor
     # This action comes from DeviseController, but because we call `sign_in`
     # manually, not skipping this action would cause a "You are already signed
     # in." error message to be shown upon successful login.
-    skip_before_action :require_no_authentication, only: [:create]
+    skip_before_action :require_no_authentication, only: [:create], raise: false
   end
 
   # Store the user's ID in the session for later retrieval and render the