nixos/postfix-tlspol: make tlsrpt depend on tlsrpt service

Without the tlsrpt service we can just fall back to QUERY and not push
around TLSRPT results.

https://github.com/Zuplu/postfix-tlspol/blob/v1.8.20/internal/server.go#L323-L329
(cherry picked from commit 9ccec77537)

nixos/modules/services/mail/postfix-tlspol.nix

@@ -8,7 +8,6 @@
 let
   inherit (lib)
     hasPrefix
-    literalExpression
     mkEnableOption
     mkIf
     mkMerge
@@ -143,7 +142,7 @@ in
               else
                 "inet:${cfg.settings.server.address}";
           in
-          [ "socketmap:${address}:QUERYwithTLSRPT" ];
+          [ "socketmap:${address}:${if config.services.tlsrpt.enable then "QUERYwithTLSRPT" else "QUERY"}" ];
       };
 
       systemd.services.postfix = {