Updating code to align with Contributor Guide template

quickstart/101-attestation-provider/variables.tf

@@ -1,9 +1,11 @@
-variable "resource_group_name" {
-  default = "myResourceGroup"
+variable "resource_group_name_prefix" {
+  default       = "rg"
+  description   = "Prefix of the resource group name that's combined with a random ID so name is unique in your Azure subscription."
 }
 
 variable "resource_group_location" {
   default = "eastus"
+  description   = "Location of the resource group."
 }
 
 variable "policy_file" {