I didn’t even realize that the Twitter and Google plus fields had been added. I was giving you instructions on how to add fields that already existed.
You can use the above technique to add any additional user contact methods. To remove or change one of the fields you can use the same hook. This code sample removes the Twitter and Google Plus. If you want to change them you first use the unset method then re add as I describe in the above post.
add_filter( 'user_contactmethods', 'update_contact_methods',10,1);
function update_contact_methods( $contactmethods ) {
unset($contactmethods['twitter']);
unset($contactmethods['googleplus']);
return $contactmethods;
}