Remove lead slash

Addresses FriendsOfPHP/PHP-CS-Fixer#705
This method should returns T_USE usages for importing. It is designed to get import statements and not lambda/trait import.
IMO it should return all T_USE for importing.

I can't see why you would like to change it @dericofilho ?
From my sample shouldn't you change `use \C\X;` into `use C\X;` as well?