DEV: Remove unnecessary debugging line

I was playing with groups locally and saw this line. I suspect this method isn't needed at all because I don't see any reference to it anywhere in the code, and as far as I know ActiveRecord objects don't have an `id!` method so if this method is called dynamically somewhere it's most likely failing.

app/models/group.rb

@@ -48,7 +48,6 @@ class Group < ActiveRecord::Base
   end
 
   def remove_review_groups
-    puts self.id!
     Category.where(review_group_id: self.id).update_all(review_group_id: nil)
     Category.where(review_group_id: self.id).update_all(review_group_id: nil)
   end