Update README.md with supported Kubernetes version

bump the Kubernetes version to 1.23.5 so folks trying this example don't run into trivial errors for unsupported old versions

Author: zioproto

README.md

@@ -35,8 +35,8 @@ module "aks" {
   resource_group_name              = azurerm_resource_group.example.name
   client_id                        = "your-service-principal-client-appid"
   client_secret                    = "your-service-principal-client-password"
-  kubernetes_version               = "1.19.3"
-  orchestrator_version             = "1.19.3"
+  kubernetes_version               = "1.23.5"
+  orchestrator_version             = "1.23.5"
   prefix                           = "prefix"
   cluster_name                     = "cluster-name"
   network_plugin                   = "azure"