Turn off all wp update notifications

function dct_remove_core_updates(){
    global $wp_version;
    return(object) array('last_checked'=> time(),'version_checked'=> $wp_version,);
}
add_filter('pre_site_transient_update_core','dct_remove_core_updates');
add_filter('pre_site_transient_update_plugins','dct_remove_core_updates');
add_filter('pre_site_transient_update_themes','dct_remove_core_updates');