doc: minor text fixes to streams.md

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.)

It appears that a `to` was left out in one sentence of the streams.md
doc. Add it.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• documentation is changed or added
• commit message follows commit guidelines