Fix etcd repository path to prevent redirects.

Signed-off-by: James Blair <mail@jamesblair.net>

Kubernetes-commit: b6c1f8ef08c3451f17048447e107c509a8ed950e

pkg/storage/etcd3/testing/testingcert/certificates.go

@@ -17,7 +17,7 @@ limitations under the License.
 package testingcert
 
 // You can use cfssl tool to generate certificates, please refer
-// https://github.com/coreos/etcd/tree/master/hack/tls-setup for more details.
+// https://github.com/etcd-io/etcd/tree/main/hack/tls-setup for more details.
 //
 // ca-config.json:
 //