Fix guides/active_record_migrations.rb template to use the current migrations version

guides/bug_report_templates/active_record_migrations.rb

@@ -31,7 +31,7 @@
 class Payment < ActiveRecord::Base
 end
 
-class ChangeAmountToAddScale < ActiveRecord::Migration[7.2]
+class ChangeAmountToAddScale < ActiveRecord::Migration::Current # or use a specific version via `Migration[number]`
   def change
     reversible do |dir|
       dir.up do