chore(ops/modules): use smtprelay from nixpkgs

This upgrades smtprelay from 1.7.0 -> 1.11.2:

- https://github.com/decke/smtprelay/releases/tag/v1.8.0
- https://github.com/decke/smtprelay/releases/tag/v1.9.0
- https://github.com/decke/smtprelay/releases/tag/v1.10.0
- https://github.com/decke/smtprelay/releases/tag/v1.11.1
- https://github.com/decke/smtprelay/releases/tag/v1.11.2

Change-Id: Ia0641f67fcc4672302a51b3ad422e447ea32b203
Reviewed-on: https://cl.tvl.fyi/c/depot/+/13115
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>

ops/modules/smtprelay.nix

@@ -47,7 +47,7 @@ in
   config = mkIf cfg.enable {
     systemd.services.smtprelay = {
       inherit description;
-      script = "${depot.third_party.smtprelay}/bin/smtprelay ${prepareArgs cfg.args}";
+      script = "${pkgs.smtprelay}/bin/smtprelay ${prepareArgs cfg.args}";
       wantedBy = [ "multi-user.target" ];
 
       serviceConfig = {

third_party/smtprelay/default.nix

@@ -1,21 +0,0 @@
-# A simple SMTP relay without the kitchen sink.
-{ pkgs, lib, ... }:
-
-pkgs.buildGoModule rec {
-  pname = "smtprelay";
-  version = "1.7.0";
-  vendorHash = "sha256:00nb81hdg5pv5l0q7w5lv08dv4v72vml7jha351frani0gpg27pn";
-
-  src = pkgs.fetchFromGitHub {
-    owner = "decke";
-    repo = "smtprelay";
-    rev = "v${version}";
-    sha256 = "0js18xhk64g0g82dx8ii8vhbbssj3pxf1hqv1zadnckdgwfwlj2r";
-  };
-
-  meta = with lib; {
-    description = "Simple Golang SMTP relay/proxy server";
-    homepage = "https://github.com/decke/smtprelay";
-    license = licenses.mit;
-  };
-}