How to Hide the "Read Only Mode" Admin Menu

function plt_hide_telchar_site_freeze_menus() {
	//Hide the "Settings → Read Only Mode" menu.
	remove_submenu_page('options-general.php', 'telchar-site-freeze');
}

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

Where do I put this code?