Update readme.txt

Author: vytisbulkevicius

readme.txt

@@ -3,7 +3,7 @@ Contributors: themeisle,codeinwp,hardeepasrani,rozroz
 Tags: rss aggregator, news aggregator, autoblogging, feed to post, rss import
 Requires at least: 6.0
 Requires PHP: 7.2
-Tested up to: 6.5
+Tested up to: 6.6
 Stable tag: trunk
 License: GPLv2 or later
 License URI: http://www.gnu.org/licenses/gpl-2.0.html