rust: avoid depreciated config

modules/rust.nix

@@ -10,13 +10,18 @@ let
     #  #"wasm32-unknown-unknown"
     #];
   };
-  rustPlatform = pkgs.makeRustPlatform {
-    cargo = rustVersion;
-    rustc = rustVersion;
-  };
+
+  # This is depreciated.
+  #rustPlatform = pkgs.makeRustPlatform {
+  #  cargo = rustVersion;
+  #  rustc = rustVersion;
+  #};
 in
 {
   environment.systemPackages = with pkgs; [
-    rustPlatform.rust.cargo
+    # This is depreciated.
+    #rustPlatform.rust.cargo
+
+    rustVersion
   ];
 }