nixos/azure: clarify how users work in basic example

nixos/maintainers/scripts/azure-new/examples/basic/system.nix

@@ -8,6 +8,9 @@ in
     "${modulesPath}/virtualisation/azure-image.nix"
   ];
 
+  ## NOTE: This is just an example of how to hard-code a user.
+  ## The normal Azure agent IS included and DOES provision a user based
+  ## on the information passed at VM creation time.
   users.users."${username}" = {
     isNormalUser = true;
     home = "/home/${username}";