Remove the legacy mailrelay variable

base/mailrelay/vars.tf

@@ -3,12 +3,6 @@ variable "instance_name" {
   type = string
 }
 
-# MSOCI-1852 - 2021-08-04 - Can be removed when old instance (instance-mailrelay.tf) is decomissioned
-variable "old_instance_name" {
-  description = "Instance name for non-authenticated server"
-  type = string
-}
-
 variable "azs" {
   type = list(string)
 }