... and pass it as the sole argument to XMLSignatureHelper::SetDateTime().

Change-Id: I7f3e8dc90bb34ca347a1ad5a79717a338af3bed9
Reviewed-on: https://gerrit.libreoffice.org/54706Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Noel Grandin <noel.grandin@collabora.co.uk>