How to hide the option to choose between username and website

Hey!

Please be sure to check out the screenshot. I want to hide the option where you can choose between the creation of a username and a site. All the clients will become a siteowner. Is it the best option to use some css? It's tricky because there are no classes. Or is it the best option to copy the wp-signup.php as a page template for my theme and delete that option.

I would love to hear your thoughts.

Thanks,
Marijn