terragrunt: removing terraform dependency (#103670)

Since terragrunt would trigger downloading all the plugins and basing on terraform 0.12 branch whereas people could use it against 0.11 or 0.13 terraform.

pkgs/applications/networking/cluster/terragrunt/default.nix

@@ -1,4 +1,4 @@
-{ lib, buildGoModule, fetchFromGitHub, makeWrapper, terraform }:
+{ lib, buildGoModule, fetchFromGitHub, makeWrapper }:
 
 buildGoModule rec {
   pname = "terragrunt";
@@ -19,11 +19,6 @@ buildGoModule rec {
 
   buildFlagsArray = [ "-ldflags=" "-X main.VERSION=v${version}" ];
 
-  postInstall = ''
-    wrapProgram $out/bin/terragrunt \
-      --set TERRAGRUNT_TFPATH ${lib.getBin terraform.full}/bin/terraform
-  '';
-
   meta = with lib; {
     description = "A thin wrapper for Terraform that supports locking for Terraform state and enforces best practices";
     homepage = "https://github.com/gruntwork-io/terragrunt/";