Clean up notification requests when deleting accounts (#29693)

app/services/delete_account_service.rb

@@ -185,6 +185,7 @@ class DeleteAccountService < BaseService
     # polymorphically associated notifications generated by this account
 
     Notification.where(from_account: @account).in_batches.delete_all
+    NotificationRequest.where(from_account: @account).in_batches.delete_all
   end
 
   def purge_favourites!