fix: OwnerID in response should be 64 character in length. (#4554)

Rather than sending a custom "minio" string, we can
change this to `sha256('arn:aws:iam::minio:user/admin')`.

Fixes #4553

cmd/event-notifier_test.go

@@ -312,7 +312,7 @@ func TestInitEventNotifier(t *testing.T) {
 	filterRules := []filterRule{
 		{
 			Name:  "prefix",
-			Value: globalMinioDefaultOwnerID,
+			Value: "minio",
 		},
 		{
 			Name:  "suffix",
@@ -535,7 +535,7 @@ func TestAddRemoveBucketListenerConfig(t *testing.T) {
 	filterRules := []filterRule{
 		{
 			Name:  "prefix",
-			Value: globalMinioDefaultOwnerID,
+			Value: "minio",
 		},
 		{
 			Name:  "suffix",