nginx.nix: don't reload nginx

Fixes #227

Reloading nginx manually is actually not needed (see
nginx-config-reload.service) and causes deadlocks.

mail-server/nginx.nix

@@ -36,7 +36,6 @@ in
     };
 
     security.acme.certs."${cfg.fqdn}".postRun = ''
-      systemctl reload nginx
       systemctl reload postfix
       systemctl reload dovecot2
     '';