[FIX] point_of_sale: random failure when reprint receipt

Because the `receiptHtml` was taken from a component which was mounted outside of the DOM, it was hardly ever destroyed for some unknown reasons and the `el.outerHTML` could not be taken to create the receipt.

closes odoo/odoo#71087

Signed-off-by: pimodoo <pimodoo@users.noreply.github.com>