The code snippets below should be pasted into your child theme's functions.php file.
Here is how you can deregister the secondary sidebar. This will remove the secondary sidebar widget area as well as the appropriate layout options in the admin.
// Remove the secondary sidebar.
add_action( 'widgets_init', 'example_widget_area' );
function example_widget_area() {
beans_deregister_widget_area( 'sidebar_secondary' );
}