doc: fix type in stream doc

Extend return type of `read()` method with `any` which is a
valid return type for readable streams in object mode.

PR-URL: https://github.com/nodejs/node/pull/21178


Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>