Add documentation for workerMachineGroups in Nutanix failure domains

docs/content/en/docs/getting-started/nutanix/nutanix-spec.md

@@ -55,7 +55,7 @@ spec:
      name: mgmt-etcd
  kubernetesVersion: "1.31"
  workerNodeGroupConfigurations:
-   - count: 1
+   - count: 3
      machineGroupRef:
        kind: NutanixMachineConfig
        name: mgmt-machine
@@ -80,20 +80,26 @@ spec:
      subnets:
        - name: vm-network-01
          type: name
+     workerMachineGroups:
+       - md-0
    - name: failure-domain-02 
      cluster:
        name: nx-cluster-02
        type: name
      subnets:
        - name: vm-network-02
          type: name
+     workerMachineGroups:
+       - md-0
    - name: failure-domain-03 
      cluster:
        name: nx-cluster-03
        type: name
      subnets:
        - name: vm-network-03
          type: name
+     workerMachineGroups:
+       - md-0
 ---
 apiVersion: anywhere.eks.amazonaws.com/v1alpha1
 kind: NutanixMachineConfig
@@ -304,6 +310,9 @@ Type to identify the failure domain subnet. (Permitted values: `name` or `uuid`)
 ### failureDomains[0].subnets[0].uuid (`failureDomains[0].subnets[0].name` or `failureDomains[0].subnets[0].uuid` required)
 UUID of the failure domain subnet.
 
+### failureDomains[0].workerMachineGroups (optional)
+List of worker machine group names that belong to a specific failure domain. See `Cluster.Spec.WorkerNodeGroupConfiguration` for more information.
+
 ## NutanixMachineConfig Fields
 
 ### cluster (required)