zlib: fix brotli flush range

Fixes: https://github.com/nodejs/node/issues/38407

PR-URL: https://github.com/nodejs/node/pull/38408


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Zijian Liu <lxxyxzj@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>