virConnectDomainEventRegisterAny: correct docs
virConnectDomainEventRegisterAny: correct docs

The callback ID can be zero, not necessarily positive; correct the
comment to reflect this.

Signed-off-by: John Levon <002e324a40ac88c85fed843304f29bb68ff6134c@movementarian.org>
Reviewed-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>

zippy2/libvirt,crobinso/libvirt,zippy2/libvirt,libvirt/libvirt,libvirt/libvirt,crobinso/libvirt,olafhering/libvirt,jfehlig/libvirt,jfehlig/libvirt,olafhering/libvirt,libvirt/libvirt,crobinso/libvirt,libvirt/libvirt,zippy2/libvirt,olafhering/libvirt,jfehlig/libvirt,crobinso/libvirt,olafhering/libvirt,zippy2/libvirt,jfehlig/libvirt