add static choice for var

main.tf

@@ -127,7 +127,7 @@ resource "aws_db_instance" "default" {
   backup_retention_period = "${var.backup_retention_period}"
   backup_window           = "${var.backup_window}"
   maintenance_window      = "${var.maintenance_window}"
-  storage_encrypted       = "${var.storage_encrypted}"
+  storage_encrypted       = "true"
   kms_key_id              = "${var.kms_key_id}"
 }