Fix etcd operator to work with k8s 1.21

Annotation `service.alpha.kubernetes.io/tolerate-unready-endpoints` stopped working in k8s 1.21
It has been deprecated for a long time, see:
https://github.com/kubernetes/kubernetes/blob/v1.21.5/pkg/controller/endpoint/endpoints_controller.go#L80
Now using the new way

pkg/util/k8sutil/k8sutil.go

@@ -21,7 +21,6 @@ import (
 	"net"
 	"net/url"
 	"os"
-	"strconv"
 	"strings"
 	"time"
 
@@ -75,7 +74,6 @@ const (
 	defaultDNSTimeout = int64(0)
 )
 
-const TolerateUnreadyEndpointsAnnotation = "service.alpha.kubernetes.io/tolerate-unready-endpoints"
 
 func GetEtcdVersion(pod *v1.Pod) string {
 	return pod.Annotations[etcdVersionAnnotationKey]
@@ -254,15 +252,12 @@ func newEtcdServiceManifest(svcName, clusterName, clusterIP string, ports []v1.S
 		ObjectMeta: metav1.ObjectMeta{
 			Name:   svcName,
 			Labels: labels,
-			Annotations: map[string]string{
-				TolerateUnreadyEndpointsAnnotation: strconv.FormatBool(publishNotReadyAddresses),
-			},
 		},
 		Spec: v1.ServiceSpec{
-			Ports:     ports,
-			Selector:  labels,
-			ClusterIP: clusterIP,
-			// PublishNotReadyAddresses: publishNotReadyAddresses, // TODO(ckoehn): Activate once TolerateUnreadyEndpointsAnnotation is deprecated.
+			Ports:                    ports,
+			Selector:                 labels,
+			ClusterIP:                clusterIP,
+			PublishNotReadyAddresses: publishNotReadyAddresses,
 		},
 	}
 	return svc