Change WooCommerce Checkout Field Optional Text

functions.php

// 2021 March
//Change "Telephone (Optional)" Text 
function change_checkout_optional_text( $fields ) {
      if( is_checkout() ) {
          $fields['billing']['billing_phone']['required'] = 'hidden';
          $fields['billing']['billing_phone']['label'] = 'Telephone (We will only use this for delivery)';
      }
      return $fields;
  } 

add_filter( 'woocommerce_checkout_fields' , 'change_checkout_optional_text', 10, 4 );