Update readme.txt

Bump version and changelog.
https://developer.woocommerce.com/2023/07/17/woocommerce-7-9-released/

Author: lukecav

readme.txt

@@ -3,9 +3,9 @@ Contributors: lukecav
 Tags:  woocommerce, performance, dashboard, orders, widgets, disable
 Requires at least: 7.2
 Tested up to: 5.6
-WC tested up to: 7.8
+WC tested up to: 7.9
 Requires PHP: 7.4
-Stable tag: 1.1.20
+Stable tag: 1.1.21
 License: GPLv2 or later
 
 Performance tweaks for the front-end and back-end of a store.
@@ -29,6 +29,9 @@ Performance tweaks related to orders on the front-end and the back-end of a stor
 
 == Changelog ==
 
+= 1.1.21 =
+Bump WooCommerce tested version.
+
 = 1.1.20 =
 Bump WooCommerce tested version.