Website: Document the final version of Org in Emacs 23.1

It will be 6.21b.  No further features, just bug fixes will go into
Emacs CVS during the pretest that is now running.

ORGWEBPAGE/index.org

@@ -61,7 +61,7 @@ releases, check this detailed list of [[file:Changes.html][user-visible changes]
 
 This package works on Emacs 23 and 22, and (with minor restrictions)
 on Emacs 21 and XEmacs 21.  Emacs 22.2 ships with Org-mode version
-4.67d.  Emacs 23.1 release is expected to ship with 6.20h.  The latest
+4.67d.  Emacs 23.1 release is expected to ship with 6.21b.  The latest
 CVS Emacs trunk usually contains a fairly recent version, but may lag
 a bit behind the website release.