You can disable all the custom post types of our theme by deactivation of XStore Core plugin. If you want to remove testimonials only then comment out line of code http://prntscr.com/d1obz2 in wp-content/plugins/et-core-plugin/et-core-plugin.php
After 3.0 update we’ll also add options for our plugin to choose what custom types you want to use.
As I have told you before after version 3.0. The new version 3.1 will include this option but don’t forget to update not just a theme but XStore Core plugin, because these options are plugin functions.