♻️ refactor system.stateVersion usage

hosts/plato/configuration.nix

@@ -175,12 +175,4 @@
       ];
     };
   };
-
-  # This value determines the NixOS release from which the default
-  # settings for stateful data, like file locations and database versions
-  # on your system were taken. It‘s perfectly fine and recommended to leave
-  # this value at the release version of the first install of this system.
-  # Before changing this value read the documentation for this option
-  # (e.g. man configuration.nix or on https://nixos.org/nixos/options.html).
-  system.stateVersion = "20.09"; # Did you read the comment?
 }