Amend runner-default example

Author: kayman-mk

examples/runner-default/variables.tf

@@ -10,14 +10,6 @@ variable "environment" {
   default     = "runners-default"
 }
 
-variable "public_ssh_key_filename" {
-  default = "generated/id_rsa.pub"
-}
-
-variable "private_ssh_key_filename" {
-  default = "generated/id_rsa"
-}
-
 variable "runner_name" {
   description = "Name of the runner, will be used in the runner config.toml"
   type        = string
@@ -31,6 +23,8 @@ variable "gitlab_url" {
 }
 
 variable "registration_token" {
+  description = "The registration token obtained from your Gitlab instance."
+  type        = string
 }
 
 variable "timezone" {