make templates user-agnostic

Templates should not reference specific users. Users are added
manually when creating a new host from the template.

templates/generic-server/users.nix

@@ -3,6 +3,7 @@
 {
   imports = [
     outputs.nixosModules.normalUsers
-    ../../users/steffen
+    # Add users here, e.g.:
+    # ../../users/<username>
   ];
 }

templates/raspberry-pi/users.nix

@@ -3,6 +3,7 @@
 {
   imports = [
     outputs.nixosModules.normalUsers
-    ../../users/steffen
+    # Add users here, e.g.:
+    # ../../users/<username>
   ];
 }