feat: enable PoCo referential_rules for ACM (terraform-google-modules#1373)

Author: apeabody

modules/acm/feature.tf

@@ -55,6 +55,7 @@ resource "google_gke_hub_feature_membership" "main" {
 
  content {
  enabled = true
+ referential_rules_enabled = true
  template_library_installed = var.install_template_library
  log_denies_enabled = var.enable_log_denies
  }