SubmittingPathces: remove Cogito reference

Removing Cogito leaves just git and StGit, which is a rather
incomplete list of git diff tools available. Sidestep the problem
of deciding what tools to mention by not mentioning any.

Signed-off-by: Sverre Rabbelier <srabbelier@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/SubmittingPatches

@@ -134,8 +134,7 @@ Another thing: NULL pointers shall be written as NULL, not as 0.
 
 (2) Generate your patch using git tools out of your commits.
 
-git based diff tools (git, Cogito, and StGIT included) generate
-unidiff which is the preferred format.
+git based diff tools generate unidiff which is the preferred format.
 
 You do not have to be afraid to use -M option to "git diff" or
 "git format-patch", if your patch involves file renames.  The