Fix flaky test for async destroying of a polymorphic belongs_to association

Author: fatkodima

activerecord/test/models/essay_destroy_async.rb

@@ -3,7 +3,7 @@
 class EssayDestroyAsync < ActiveRecord::Base
   self.table_name = "essays"
   belongs_to :book, dependent: :destroy_async, class_name: "BookDestroyAsync"
-  belongs_to :writer, primary_key: :name, polymorphic: true, dependent: :destroy_async
+  belongs_to :writer, polymorphic: true, dependent: :destroy_async
 end
 
 class LongEssayDestroyAsync < EssayDestroyAsync