fix: adjust logic for admin password

Co-authored-by: Copilot <[email protected]>

Author: RoseSecurity

src/cluster-regional.tf

@@ -16,7 +16,7 @@ module "aurora_postgres_cluster" {
   cluster_size               = var.cluster_size
   promotion_tier             = var.promotion_tier
   admin_user                 = local.admin_user
-  admin_password             = var.manage_admin_user_password != null ? null : local.admin_password
+  admin_password             = var.manage_admin_user_password ? null : local.admin_password
   manage_admin_user_password = var.manage_admin_user_password
 
   db_name                              = local.database_name