[racket] red underline of language name

Thanks, though I'm not sure that was my main point.  Though I now see
that "planet" really is considered a whole language in its own right,
so I guess this red underlining is inevitable by the semantics.

Incidentally, for those who find this thread later, there's another
option you will may useful after you employ Danny's advice:

   --redirect-main http://docs.racket-lang.org/

This makes the documentation point to the Racket docs site rather than
to a path on your location machine (which are not paths you usually
want to publish to the world).

Shriram