remove experiments

main.tf

@@ -1,13 +1,12 @@
 terraform {
   backend "local" {}
-  required_version = ">= 0.13"
+  required_version = ">= 0.15"
   required_providers {
     kubernetes = {
       source  = "hashicorp/kubernetes"
       version = "2.3.2"
     }
   }
-  experiments = [module_variable_optional_attrs]
 }