doc: make it more exact

[MoonBall]

I made a comment on every change.

Checklist

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

Affected core subsystem(s)

stream

[MoonBall]

only calling unpipe() will make stream to paused mode. see the following example.

const { Readable, Writable } = require('stream');

const r = new Readable();
const w = new Writable();

r._read = () => {};
w._write = () => {};

r.pipe(w);
r.on('data', () => {});

r.unpipe();
console.log(r._readableState.flowing); // the output is false

[jasnell]

quick grammar nit on this: by removing all pipe destinations by ... the sentence should be something like:

Multiple pipe destinations may be removed by calling the [`stream.unpipe()`][] method.

[MoonBall]

fixed.

[MoonBall]

Emitting a 'drain' event need to meet more conditions. See the source code of writable stream.

[Trott]

maybe will -> might

[MoonBall]

fixed.

[maclover7]

Docs CI: https://ci.nodejs.org/job/node-test-pull-request-lite/128/

[BridgeAR]

Landed in 3ca7935