terraform: ephemeral tag to help with automated teardown (#48336)

(cherry picked from commit 8ae8d12)

Author: v1v

x-pack/metricbeat/module/aws/terraform.tf

@@ -12,6 +12,7 @@ provider "aws" {
       org          = "obs"
       team         = "cloud-monitoring"
       project      = "metricbeat_aws-ci"
+      ephemeral    = "true"
     }
   }
 }