request review task attachments are stored in workflow task item.

so within request review action you have to configure to "Store task IDs in" into a collection variable.

then loop through the collection, query task list for given task items and the attachment URLs from them.

here is described an approach how to do that from list item - collect task attachments in list item and show all attachments in next task 

you will need to do moreless the same from task item.