On a single product page, WooCommerce shows related products by default. Here’s the code snippet you need to put in your theme’s functions.php in order to disable this feature:
/* Remove WooCommerce Related Products */
add_filter('woocommerce_product_related_posts_query', '__return_empty_array', 100);
If you’re using a theme designed specifically for WooCommerce, you might be able to remove the related posts without any code by using the theme customizer.