pack-objects: drop unused parameter from oe_map_new_pack()

pack-objects: drop unused parameter from oe_map_new_pack()

Since 43fa44fa3b (pack-objects: move in_pack out of struct object_entry,
2018-04-14), we store the source pack for each object as a small index
rather than as a pointer. When we see a new pack that has no allocated
index, we fall back to generating an array of pointers by calling
oe_map_new_pack().

Perhaps counter-intuitively, that function does not need to actually see
our new index-less pack. It only allocates and populates the array with
the existing packs, after which oe_set_in_pack() actually adds the new
pack to the array.

Let's drop the unused "struct packed_git" argument to oe_map_new_pack()
to avoid confusion.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>