Update dex_secret_key variable to set default value to null

Author: karimzakzouk

Terraform/modules/argocd/variables.tf

@@ -59,6 +59,6 @@ variable "dex_secret_key" {
   description = "Dex server secret key for ArgoCD (production)"
   type        = string
   sensitive   = true
-  default     = random_password.dex_secret.result
+  default     = null
 }