Hello World KubeVirt VM example yaml is incorrect

Fix yaml file.

Closes-bug: 2078817

Change-Id: If7561855925d0e7fafbdf45fc2bbab5702e609b5
Signed-off-by: Elisamara Aoki Goncalves <elisamaraaoki.goncalves@windriver.com>

doc/source/kube-virt/hello-world-kubevirt-vm-05503659173c.rst

@@ -45,21 +45,19 @@ the |VM| via the console:
       apiVersion: kubevirt.io/v1
       kind: VirtualMachine
       metadata:
-        labels:
-          kubevirt.io/vm: vm-cirros
         name: vm-cirros
       spec:
         running: false
         template:
           metadata:
             labels:
-              kubevirt.io/vm: vm-cirros
+              kubevirt.io/domain: vm-cirros
           spec:
             domain:
+              cpu:
+                cores: 1
               devices:
                 disks:
-            -disk:
-               bus: virtio
                 - name: containerdisk
                   disk:
                     bus: virtio