[REF] pos, pos_*: Change Escpos' XML to HTML

Receipt are now printed as JPGs so receipts need to be formatted as
classic HTML to be rendered as images by Wkhtmltoimage.

There were two versions of the receipt for an order. The one in XML,
to be printed, and the one in HTML, that was displayed in the POS.
Since both of them are now HTML, we can remove one of them.

TaskID: 1939455