Do not suggest that --exclude-promisor-objects is supported by git-log,
since it currently BUG-crashes and it's not necessary to support it.
Options that control behavior for promisor objects should be limited to
a small number of commands.
Signed-off-by: Matthew DeVore <matvore@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>