Remove initializers feature gate (#14602)

* Remove initializers feature gate

Initializers are removed in 1.14
kubernetes/kubernetes#72972

* Update feature-gates.md

content/en/examples/examples_test.go

@@ -89,9 +89,6 @@ func validateObject(obj runtime.Object) (errors field.ErrorList) {
 	// Enable CustomPodDNS for testing
 	utilfeature.DefaultFeatureGate.Set("CustomPodDNS=true")
 	switch t := obj.(type) {
-	case *admissionregistration.InitializerConfiguration:
-		// cluster scope resource
-		errors = ar_validation.ValidateInitializerConfiguration(t)
 	case *api.ConfigMap:
 		if t.Namespace == "" {
 			t.Namespace = api.NamespaceDefault