Hide Coupon on checkout page if a coupon is already applied

functions.php

<?php
/*
* source: https://wpglorify.com/?p=3846
 * Hide coupon notice on the checkout page if a coupon has been applied in cart
 */
add_filter( 'woocommerce_coupons_enabled', 'woocommerce_coupons_enabled_checkout' );
function woocommerce_coupons_enabled_checkout( $coupons_enabled ) {
  
    global $woocommerce;
    
    if ( ! empty( $woocommerce->cart->applied_coupons ) ) {
        return false;
    }
    return $coupons_enabled;
}