/**
 * Hide WordPress update nag to all but admins
 */
 
function hide_update_notice_to_all_but_admin() {
    if ( !current_user_can( 'update_core' ) ) {
        remove_action( 'admin_notices', 'update_nag', 3 );
    }
}
add_action( 'admin_head', 'hide_update_notice_to_all_but_admin', 1 );