Use the following code to hide the update message to all users except Admin users. From Paulund's blog: http://www.paulund.co.uk/hide-wordpress-update-notice

WP_hide_update_notice

function hide_update_notice_to_all_but_admin_users() 
{
    if (!current_user_can('update_core')) {
        remove_action( 'admin_notices', 'update_nag', 3 );
    }
}
add_action( 'admin_notices', 'hide_update_notice_to_all_but_admin_users', 1 );