Use line_item price instead of variant price in return_authorization

[sanemat]

The case of return authorization, not variant.price but line_items.first.price to use.

[radar]

I don't understand why this pull request is necessary. In what case would you want to be returning an entire line item rather than just one item contained within that line item?

[sanemat]

In admin/orders/_form, admin/shared/_order_details, admin/orders/_add_product use line_items(price at the time), but admin/return_authorizations/_form uses current variant price, I want to use price at the time in return authorization case.
inventory unit does not have price at the time, line item has price at the time.

[radar]

Ok, I see your point now. Thanks for explaining it.