Do not print "log" and "shortlog" redundantly in commit
view. This is passed into the $extra argument of
git_print_page_nav from git_commit, but git_print_page_nav
prints "log" and "shortlog" already with the same head.
Noticed by Junio.
Signed-off-by: Luben Tuikov <ltuikov@yahoo.com> Signed-off-by: Junio C Hamano <junkio@cox.net>