UX: drop the automatic_membership_retroactive column from groups model. (#9430)

config/routes.rb

@@ -94,6 +94,7 @@ Discourse::Application.routes.draw do
         get 'bulk'
         get 'bulk-complete' => 'groups#bulk'
         put 'bulk' => 'groups#bulk_perform'
+        put "automatic_membership_count" => "groups#automatic_membership_count"
       end
       member do
         put "owners" => "groups#add_owners"