nixos/lib/testing: remove another source of unnecessary test rebuilds

      # The human version (e.g. 21.05-pre) is left as is, because it is useful

      # for external modules that test with e.g. testers.nixosTest and rely on that

      # version number.

      config.system.nixos.revision = mkForce "constant-nixos-revision";

      config.system.nixos = {

        revision = mkForce "constant-nixos-revision";

        label = mkForce "test";

      };

    }

  ];