reorder_woo_product_data_tab.php

<?php
/**
 * Reorder woocommerce product data tabs
 */
add_filter( 'woocommerce_product_tabs', 'woo_reorder_product_data_tabs', 98 );
function woo_reorder_product_data_tabs( $tabs ) {

	$tabs['reviews']['priority'] = 5;			// Reviews first
	$tabs['description']['priority'] = 10;			// Description second
	$tabs['additional_information']['priority'] = 15;	// Additional information third

	return $tabs;
}