MyFirstObjectWalk: fix filtered object walk
Commit
f0d2f84919 (MyFirstObjectWalk: update recommended usage,
2022-03-09) changed a call of parse_list_objects_filter() in a way
that probably never worked: parse_list_objects_filter() always needed
a pointer as its first argument.
Fix this by removing the CALLOC_ARRAY and passing the address of
rev->filter to parse_list_objects_filter() in accordance to
such a call in revisions.c, for example.
Signed-off-by: Dirk Gouders <dirk@gouders.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>