Remove insecure output of creds, adjust README

terraform/bootstrap/main.tf

@@ -14,7 +14,3 @@ resource "cloudfoundry_service_key" "bucket_creds" {
   name             = "${local.s3_service_name}-access"
   service_instance = module.s3.bucket_id
 }
-
-output "bucket_credentials" {
-  value = cloudfoundry_service_key.bucket_creds.credentials
-}