Update tested version to 6.9

Author: vytisbulkevicius

readme.txt

@@ -2,7 +2,7 @@
 Contributors: codeinwp, themeisle
 Tags: menu, nav-menu, icons, navigation
 Requires at least: 4.7
-Tested up to: 6.8
+Tested up to: 6.9
 Stable tag: trunk
 License: GPLv2
 License URI: http://www.gnu.org/licenses/gpl-2.0.html