git-zip-tree can be safely removed because it was never part of a formal
release. This patch makes 'git-archive --format=zip' the one and only git
ZIP file creation command.
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <junkio@cox.net>