doc: stream write(chunk, encoding, cb) encoding can be null

[dev-script]

In stream write encoding can be null.

Fixes: #33715

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• documentation is changed or added
• commit message follows commit guidelines

[mscdex]

The targeted subsystem in the commit message should be doc instead of stream.

[dev-script]

The targeted subsystem in the commit message should be doc instead of stream.

I have done changes. please review

[lpinca]

Any falsy value for the encoding argument works in the same way.

node/lib/internal/streams/writable.js

Lines 293 to 294 in ee9e3e7

	if (!encoding)
	encoding = state.defaultEncoding;

Not sure if it is ok to add only null.

[aduh95]

Landed in caa5a05