Fix deprecated interpolation-only expression (#594)

CHANGELOG.md

@@ -16,6 +16,7 @@ project adheres to [Semantic Versioning](http://semver.org/).
 ### Changed
 
 - Updated instance_profile_names and instance_profile_arns outputs to also consider launch template as well as asg (by @ankitwal)
+- Fix deprecated interpolation-only expression (by @angelabad)
 
 # History
 

kubectl.tf

@@ -1,6 +1,6 @@
 resource "local_file" "kubeconfig" {
   count    = var.write_kubeconfig ? 1 : 0
   content  = data.template_file.kubeconfig.rendered
-  filename = "${substr(var.config_output_path, -1, 1) == "/" ? "${var.config_output_path}kubeconfig_${var.cluster_name}" : var.config_output_path}"
+  filename = substr(var.config_output_path, -1, 1) == "/" ? "${var.config_output_path}kubeconfig_${var.cluster_name}" : var.config_output_path
 }