This update simplifies the payment process for self-order POS systems. Due to a recent update in the core Odoo platform (odoo/odoo#231190), payment code previously specific to self-order POS is no longer needed. The updated code now leverages shared payment code from the standard POS module, streamlining operations and reducing complexity.

Since odoo/odoo#231190, payment terminals can now share the same code between the POS and the Kiosk. This means payment code in `pos_self_order_iot` can be removed, since the code from `pos_iot` can be used instead.