Revert "mcumgr-client.updateScript: drop"

This reverts commit eecd125.

The update script should work now, because upstream includes a
lockfile.

Author: alyssais

pkgs/by-name/mc/mcumgr-client/package.nix

@@ -2,6 +2,7 @@
   lib,
   rustPlatform,
   fetchFromGitHub,
+  nix-update-script,
   pkg-config,
   udev,
   stdenv,
@@ -21,6 +22,8 @@ rustPlatform.buildRustPackage rec {
 
   cargoHash = "sha256-9jlthe7YQJogcjGv+TOk+O2YW3Xrq6h9tTjXdKHG99k=";
 
+  passthru.updateScript = nix-update-script { };
+
   nativeBuildInputs = [ pkg-config ];
 
   buildInputs =