Fix kubecost version

Author: niallthomson

manifests/modules/observability/kubecost/.workshop/terraform/vars.tf

@@ -38,5 +38,5 @@ variable "kubecost_chart_version" {
   description = "The chart version of kubecost to use"
   type        = string
   # renovate-helm: depName=cost-analyzer registryUrl=https://kubecost.github.io/cost-analyzer
-  default = "2.8.6"
-}
+  default = "2.8.4"
+}