nixos/zram: prevent implicitly disabling negative-sized ZRAM (#444426)

      memoryPercent = lib.mkOption {

        default = 50;

        type = lib.types.int;

        type = lib.types.ints.positive;

        description = ''

          Maximum total amount of memory that can be stored in the zram swap devices

          (as a percentage of your total memory). Defaults to 1/2 of your total