How to hide Discount code in Magento 2
Here is the info how you can get rid off Discount code from cart page and payment page. Add below css code and it will hide discount code from the pages.
For cart page :
.checkout-cart-index .cart-discount {display: none;}
For payment page :
.checkout-index-index .payment-option._collapsible.opc-payment-additional.discount-code {
display: none;
}