Remove `~<...~>` in GENERATE-SCALE for portability.

In VSPARK, function GENERATE-SCALE depends on format control `~<...~>`.
But `~<...~>` is bit implementation dependent.
For example,
```common-lisp
SBCL> (format nil "~30,,,'-<~A~;~A~;~A~>" 11 222 33)
=> "11-----------222------------33"
CCL>  (format nil "~30,,,'-<~A~;~A~;~A~>" 11 222 33)
=> "11------------222-----------33"
```