numa: drop support for '-numa node' (without memory specified)

it was deprecated since 4.1
commit 4bb4a273 (numa: deprecate implict memory distribution between nodes)

Users of existing VMs, wishing to preserve the same RAM distribution,
should configure it explicitly using ``-numa node,memdev`` options.
Current RAM distribution can be retrieved using HMP command
`info numa` and if separate memory devices (pc|nv-dimm) are present
use `info memory-device` and subtract device memory from output of
`info numa`.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Message-Id: <20200911084410.788171-2-imammedo@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>