ls-remote documentation: <refs> argument is optional
ls-remote documentation: <refs> argument is optional

Correct SYNOPSIS section.

Signed-off-by: Piotr Krukowiecki <16c965353adfd7b0e823126286eefb66be92c7f6@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git