Update readme.txt

Bump WooCommerce tested version.
https://developer.woocommerce.com/2021/09/24/woocommerce-5-7-1-fix-release/

Author: lukecav

readme.txt

@@ -3,7 +3,7 @@ Contributors: lukecav
 Tags:  woocommerce, performance, dashboard, orders, widgets, disable
 Requires at least: 5.0
 Tested up to: 5.8.1
-WC tested up to: 5.7.0
+WC tested up to: 5.7.1
 Requires PHP: 7.3
 Stable tag: 1.1.1
 License: GPLv2 or later