How to Hide the "WP Middle Post Content" Admin Menu

function plt_hide_wp_middle_post_content_menus() {
	//Hide the "Settings → WP Middle Post Content" menu.
	remove_submenu_page('options-general.php', 'wp-middle-post-content');
}

add_action('admin_menu', 'plt_hide_wp_middle_post_content_menus', 11);

Where do I put this code?