Change the H2 tag on the related products heading to div tag - Related Products for WooCommerce (https://wordpress.org/plugins/wt-woocommerce-related-products/)

functions.php

<?php // do not copy this line

add_filter('wt_related_products_heading', 'wt_crp_alter_title_tag');
function wt_crp_alter_title_tag($title) {
	$title = preg_replace("/<h2>(.+?)<\/h2>/is", "<div>$1</div>", $title);

	return $title;
}