Remove irrelevant reference from "Tying it all together"

Sorry Jon, but this might not be of any help to new Git users ;)

Acked-by: Jon Loeliger <jdl@jdl.com>
Signed-off-by: Thomas Ackermann <th.acker@arcor.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/user-manual.txt

@@ -3924,8 +3924,7 @@ save the note about that state, in practice we tend to just write the
 result to the file pointed at by `.git/HEAD`, so that we can always see
 what the last committed state was.
 
-Here is an ASCII art by Jon Loeliger that illustrates how
-various pieces fit together.
+Here is a picture that illustrates how various pieces fit together:
 
 ------------