get rid of string interpolation warning

Author: vavdoshka

modules/merge/outputs.tf

@@ -1,4 +1,4 @@
 output "container_definitions" {
   description = "A list of container definitions in JSON format that describe the different containers that make up your task"
-  value       = "${format("[%s]", join(",", var.container_definitions))}"
+  value       = format("[%s]", join(",", var.container_definitions))
 }