OCPBUGS-30135: fix "OpenShiftSDN deprecated" error message

The error message

```
time="2024-03-01T14:37:25Z" level=error msg="failed to fetch Master Machines: failed to load asset \"Install Config\": failed to create install config: invalid \"install-config.yaml\" file: networking.networkType: Invalid value: \"OpenShiftSDN\": networkType OpenShiftSDN is deprecated, please use OVNKubernetes"
```

is misleading, as "deprecated" means "we'll still do it, but we'll
grumble about it". Fix.

OCPBUGS-30135

Author: 2uasimojo

pkg/types/validation/installconfig.go

@@ -379,7 +379,7 @@ func validateNetworking(n *types.Networking, singleNodeOpenShift bool, fldPath *
 	}
 
 	if n.NetworkType == string(operv1.NetworkTypeOpenShiftSDN) {
-		allErrs = append(allErrs, field.Invalid(fldPath.Child("networkType"), n.NetworkType, "networkType OpenShiftSDN is deprecated, please use OVNKubernetes"))
+		allErrs = append(allErrs, field.Invalid(fldPath.Child("networkType"), n.NetworkType, "networkType OpenShiftSDN is not supported, please use OVNKubernetes"))
 	}
 
 	if len(n.MachineNetwork) > 0 {

pkg/types/validation/installconfig_test.go

@@ -564,7 +564,7 @@ func TestValidateInstallConfig(t *testing.T) {
 				c.Networking.ClusterNetworkMTU = 8000
 				return c
 			}(),
-			expectedError: `networking.networkType: Invalid value: "OpenShiftSDN": networkType OpenShiftSDN is deprecated, please use OVNKubernetes, networking.clusterNetworkMTU: Invalid value: 8000: cluster network MTU is not valid with network plugin OpenShiftSDN`,
+			expectedError: `networking.networkType: Invalid value: "OpenShiftSDN": networkType OpenShiftSDN is not supported, please use OVNKubernetes, networking.clusterNetworkMTU: Invalid value: 8000: cluster network MTU is not valid with network plugin OpenShiftSDN`,
 		},
 		{
 			name: "missing control plane",
@@ -1700,7 +1700,7 @@ func TestValidateInstallConfig(t *testing.T) {
 
 				return c
 			}(),
-			expectedError: "[networking.networkType: Invalid value: \"OpenShiftSDN\": networkType OpenShiftSDN is deprecated, please use OVNKubernetes, platform.baremetal.ingressVIPs: Invalid value: \"10.0.0.4\": IP expected to be in one of the machine networks: ffd0::/48]",
+			expectedError: "[networking.networkType: Invalid value: \"OpenShiftSDN\": networkType OpenShiftSDN is not supported, please use OVNKubernetes, platform.baremetal.ingressVIPs: Invalid value: \"10.0.0.4\": IP expected to be in one of the machine networks: ffd0::/48]",
 		},
 		{
 			name: "ingressvips_v6_on_openshiftsdn",
@@ -1716,7 +1716,7 @@ func TestValidateInstallConfig(t *testing.T) {
 
 				return c
 			}(),
-			expectedError: "[networking.networkType: Invalid value: \"OpenShiftSDN\": networkType OpenShiftSDN is deprecated, please use OVNKubernetes, platform.baremetal.apiVIPs: Invalid value: \"10.0.0.5\": IP expected to be in one of the machine networks: ffd0::/48]",
+			expectedError: "[networking.networkType: Invalid value: \"OpenShiftSDN\": networkType OpenShiftSDN is not supported, please use OVNKubernetes, platform.baremetal.apiVIPs: Invalid value: \"10.0.0.5\": IP expected to be in one of the machine networks: ffd0::/48]",
 		},
 		{
 			name: "too_many_apivips",