WooCommerce: remove repeated featured image from product gallery

woocommerce-remove-repeated-featured-image.php

<?php

add_filter('woocommerce_single_product_image_thumbnail_html', 'app_remove_repeated_featured_image_from_product_gallery', 10, 2);
function app_remove_repeated_featured_image_from_product_gallery( $html, $attachment_id ) {
        global $product;
        static $counter = 0;

        if ( get_post_thumbnail_id( $product->get_id() ) == $attachment_id ) {
                $counter++;

                if ( $counter > 1 ) {
                        return '';
                }
        }

        return $html;
}