Revert "Also use 'track_object_refs = 0' in update-server-info."

This reverts d119e3de commit.

Object references are used in server-info.c:find_pack_info_one() to
find out which objects in the pack are heads, therefore tracking of
references cannot be disabled.
Signed-off-by: NSergey Vlasov <vsu@altlinux.ru>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

update-server-info.c

 #include "cache.h"
-#include "object.h"
 
 static const char update_server_info_usage[] =
 "git-update-server-info [--force]";
@@ -8,8 +7,6 @@ int main(int ac, char **av)
 {
 	int i;
 	int force = 0;
-	track_object_refs = 0;
-
 	for (i = 1; i < ac; i++) {
 		if (av[i][0] == '-') {
 			if (!strcmp("--force", av[i]) ||