Remove useless depth argument from static function cups_get_printer_uri

Remove useless depth argument from static function cups_get_printer_uri

This is safe to do since this function is not supposed to be exposed via the ABI, nor is there a pointer to this function, so as long as every other function in the file accommodates this change, no behavioral change should happen.

In addition, depth is always 0 and only used for one debug print statement anyway, so we can and should remove it, instead of simply declaring it unused.