Use autoDestroy when it lands in readable-stream (node 11.2.0)

See [`autoDestroy`](https://nodejs.org/api/stream.html#stream_new_stream_readable_options):

> Whether this stream should automatically call `.destroy()` on itself after ending. 

I think that can replace:

https://github.com/Level/iterator-stream/blob/d59b13a9ef3ae7862c7a8e9262d7d7c417e067df/index.js#L16