index-pack: correct install_packed_git() args

The function does not start taking the repository object as a
parameter before v2.18 track.  Make the topic mergeable to v2.17
maintenance track by dropping it.

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

builtin/index-pack.c

@@ -1484,7 +1484,7 @@ static void final(const char *final_pack_name, const char *curr_pack_name,
 		struct packed_git *p;
 		p = add_packed_git(final_index_name, strlen(final_index_name), 0);
 		if (p)
-			install_packed_git(the_repository, p);
+			install_packed_git(p);
 	}
 
 	if (!from_stdin) {