Update readme.txt

Bump PHP version to 7.3.

Author: lukecav

readme.txt

@@ -4,7 +4,7 @@ Tags:  woocommerce, performance, dashboard, orders, widgets, disable
 Requires at least: 5.0
 Tested up to: 5.4.1
 WC tested up to: 4.1.1
-Requires PHP: 7.2
+Requires PHP: 7.3
 Stable tag: 1.0.8
 License: GPLv2 or later