[FIX] pos_loyalty: gift card reward should not have taxes

Current behavior:
When using a gift card in the PoS, you would get 2 gift card reward
lines, one positive and one negative. Wich should not be the case.
This happens because the gift card reward had taxes.
To fix this we need to remove the taxes from the gift card reward,
as it is done in the sale_loyalty module ´_get_reward_values_discount´
https://github.com/odoo/odoo/blob/30062210cc879a1d2349b888a510f29ea40d5920/addons/sale_loyalty/models/sale_order.py#L313

Steps to reproduce:
- Install the pos_loyalty module
- Open PoS
- Buy a gift card and copy the code
- Buy a product and pay with the gift card
- You will see 2 gift card reward lines, one positive and one negative

opw-3472830

closes odoo/odoo#133034

X-original-commit: 7814bb2663ac75ef91922897b88022d87f58241f
Signed-off-by: Joseph Caburnay (jcb) <jcb@odoo.com>
Signed-off-by: Robin Engels (roen) <roen@odoo.com>

addons/pos_loyalty/static/src/overrides/models/loyalty.js

@@ -1298,6 +1298,7 @@ patch(Order.prototype, {
                     points_cost: pointCost,
                     reward_identifier_code: rewardCode,
                     merge: false,
+                    tax_ids: [],
                 },
             ];
         }