Update comment on L2 connectivity checks and MachineNetworks

OpenShift has ~always supported having machines in multiple
machineNetworks, so update the TODO comment to reflect that accounting
for this is already something we need to do to fully support
non-UserManagedNetworking clusters. (UserManagedNetworking clusters use
only the L3 connectivity check.)

See https://issues.redhat.com/browse/OCPBUGS-30730 for more details.

internal/host/validator.go

@@ -667,8 +667,9 @@ func (v *validator) belongsToL2MajorityGroup(c *validationContext, majorityGroup
 		return ValidationPending
 	}
 
-	// TODO(mko) This rule should be revised as soon as OCP supports multiple machineNetwork
-	//           entries using the same IP stack.
+	// TODO(mko) This rule must be revised to support multiple machineNetwork
+	//           entries using the same IP stack on clusters without
+	//           user-managed networking. (OCPBUGS-30730)
 	areNetworksEqual := func(ipnet1, ipnet2 *net.IPNet) bool {
 		return ipnet1.IP.Equal(ipnet2.IP) && bytes.Equal(ipnet1.Mask, ipnet2.Mask)
 	}