doc: standardize versions in stream module doc

Refer to Node.js versions without a prepended `v`. This was standardized
on previously to avoid confusion between Node.js 8 and the V8 JavaScript
engine. (`Node.js 8` is clear. `v8` or even `Node.js v8`, not so much.)

PR-URL: https://github.com/nodejs/node/pull/23306


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>