mailmanPackages.python.pkgs.hiredis: fix override (NixOS#374572)

Author: SuperSandro2000

pkgs/servers/mail/mailman/python.nix

@@ -24,7 +24,7 @@ lib.fix (self: python3.override {
       hiredis = super.hiredis.overrideAttrs (new: { src, ... }: {
         version = "3.1.0";
         src = src.override {
-          rev = "refs/tags/v${new.version}";
+          tag = new.version;
           hash = "sha256-ID5OJdARd2N2GYEpcYOpxenpZlhWnWr5fAClAgqEgGg=";
         };
       });