Fix small typo in cluster-install readme (aws-samples#319)

Author: minamijoyo

cluster-install/readme.adoc

@@ -269,7 +269,7 @@ ip-172-20-93-220.eu-central-1.compute.internal  node    True
 Your cluster example.cluster.k8s.local is ready
 ```
 
-It is also possible to create a DNS-based cluster where the master and worker nodes are in private subnets. For more information about creating DNS-based clusterssee Appendix: Create a DNS-based Kubernetes cluster below.
+It is also possible to create a DNS-based cluster where the master and worker nodes are in private subnets. For more information about creating DNS-based clusters, see Appendix: Create a DNS-based Kubernetes cluster below.
 If `--dns private` is also specified, a Route53 private hosted zone is created for routing the traffic for the domain within one or more VPCs. The Kubernetes API can therefore only be accessed from within the VPC. This is a current issue with kops (see https://github.com/kubernetes/kops/issues/2032). A possible workaround is to mirror the private Route53 hosted zone with a public hosted zone that exposes only the API server ELB endpoint. This workaround is discussed http://kubecloud.io/setup-ha-k8s-kops/[here].
 
 Although most of the exercises in this workshop should work on a cluster with a private VPC, some commands won't, specifically those that use a proxy to access internally hosted services.