MAINTAINERS: new kvmarm mailing list

KVM/arm64 development is moving to a new mailing list (see
https://lore.kernel.org/all/20221001091245.3900668-1-maz@kernel.org/);


kvm-unit-tests should advertise the new list as well.

Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Andrew Jones <andrew.jones@linux.dev>