How can I remove the new stats message? [closed]

The next level up would be an inline style in the head using a hook in a dedicated plugin or theme functions.php:

function add_admin_css(){
    ?><style>.gotonewdash {display: none;}</style><?php
}
add_action( 'admin_head','add_admin_css');

Next level up after that would be an admin.css in a plugin with is_admin() and wp_enqueue_style