git(1): remove a defunct link to "list of authors"

The linked page has not been showing the promised "more complete
list" for more than 6 months by now, and nobody has resurrected
the list there nor elsewhere since then.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git.txt

@@ -868,8 +868,7 @@ Authors
 -------
 Git was started by Linus Torvalds, and is currently maintained by Junio
 C Hamano. Numerous contributions have come from the git mailing list
-<git@vger.kernel.org>. For a more complete list of contributors, see
-http://git-scm.com/about. If you have a clone of git.git itself, the
+<git@vger.kernel.org>.  If you have a clone of git.git itself, the
 output of linkgit:git-shortlog[1] and linkgit:git-blame[1] can show you
 the authors for specific parts of the project.