fix: added sensitive flag to the api_key output (#67)

Terraform was throwing below error related to sensitive
value of api_key

---
│ Error: Output refers to sensitive values
│
│   on outputs.tf line 16:
│   16: output "api_key" {
│
│ To reduce the risk of accidentally exporting sensitive data that was
│ intended to be only internal, Terraform requires that any root module
│ output containing sensitive data be explicitly marked as sensitive, to
│ confirm your intent.
│
│ If you do intend to export this data, annotate the output value as
│ sensitive by adding the following argument:
│     sensitive = true
---

Co-authored-by: Vikas Kumar <[email protected]>

outputs.tf

@@ -16,4 +16,5 @@ output "allowed_ip_addresses" {
 output "api_key" {
   value       = data.azurerm_function_app_host_keys.function.default_function_key
   description = "Created Default Functions API Key"
-}
+  sensitive   = true
+}