update readme

Author: tillkruss

readme.txt

@@ -72,7 +72,7 @@ Redis Object Cache has various WP CLI commands, for more information run `wp hel
 - Call `redis_object_cache_error` action before `wp_die()`
 - Allow `WP_REDIS_PLUGIN_PATH` to be defined elsewhere
 - Added experimental flush timeout (defaults to `5` seconds)
-- Swap out ignored `themes` for `theme_json` cache group
+- Dropped unnecessary default ignored groups
 
 = 2.4.4 =