Fixed reference to cluster_description

gke.tf

@@ -8,7 +8,7 @@ resource "google_container_cluster" "primary" {
   remove_default_node_pool = true
   initial_node_count       = 1
   min_master_version       = "1.19"
-  description              = var.description
+  description              = var.cluster_description
 }
 
 resource "google_container_node_pool" "primary_preemptible_nodes" {