patchAdd missing -z to git check-attr usage text for consistency with man page

> Signed-off-by: Adam Spiers <git@adamspiers.org>
> ---
>  builtin/check-attr.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/builtin/check-attr.c b/builtin/check-attr.c
> index e1ff575..075d01d 100644
> --- a/builtin/check-attr.c
> +++ b/builtin/check-attr.c
> @@ -9,7 +9,7 @@ static int cached_attrs;
>  static int stdin_paths;
>  static const char * const check_attr_usage[] = {
>  N_("git check-attr [-a | --all | attr...] [--] pathname..."),
> -N_("git check-attr --stdin [-a | --all | attr...] < <list-of-paths>"),
> +N_("git check-attr --stdin [-z] [-a | --all | attr...] < <list-of-paths>"),
>  NULL
>  };