All currently supported versions of AR defines each_counter_cached_associations

This `defined?(super)` check was introduced for Rails 4.1 support
https://github.com/rubysherpas/paranoia/pull/390#issuecomment-284819747
but we've stopped supporting Rails 4.1 already
https://github.com/rubysherpas/paranoia/pull/393#issuecomment-289227091

lib/paranoia.rb

@@ -174,7 +174,7 @@ module Paranoia
   private
 
   def each_counter_cached_associations
-    !(defined?(@_disable_counter_cache) && @_disable_counter_cache) && defined?(super) ? super : []
+    !(defined?(@_disable_counter_cache) && @_disable_counter_cache) ? super : []
   end
 
   def paranoia_restore_attributes