hpcg: apply nixfmt

pkgs/by-name/hp/hpcg/package.nix

···
-{ lib, stdenv, fetchurl, mpi } :
+{
+  lib,
+  stdenv,
+  fetchurl,
+  mpi,
+}:
 
 stdenv.mkDerivation rec {
   pname = "hpcg";
···
     mainProgram = "xhpcg";
   };
 }
-