Update tags.tf

added is_cost_tracking boolean and marked as optional.

Author: rramge

docs/examples/identity/tags.tf

@@ -13,6 +13,8 @@ resource "oci_identity_tag" "tag1" {
   name             = "tf-example-tag"
   tag_namespace_id = "${oci_identity_tag_namespace.tag-namespace1.id}"
 
+  #Optional
+  is_cost_tracking = false          // default is "false". The value "true" is only permitted if the associated tag namespace is part of the root compartment. 
   is_retired = false
 }