doc: remove unclear text from fs.write()

There is a paragraph explaining that `fs.write()` cannot write a
substring of the provided string. It's not clear what `buffer` refers
to in that paragraph or even what the purpose of the paragraph is.
There's no suggestion elsewhere that `fs.write()` should be expected to
have a substring feature. Remove the paragraph.

PR-URL: #20450
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/fs.md

@@ -3233,10 +3233,6 @@ The callback will receive the arguments `(err, written, string)` where `written`
 specifies how many _bytes_ the passed string required to be written. Note that
 bytes written is not the same as string characters. See [`Buffer.byteLength`][].
 
-Unlike when writing `buffer`, the entire string must be written. No substring
-may be specified. This is because the byte offset of the resulting data may not
-be the same as the string offset.
-
 Note that it is unsafe to use `fs.write` multiple times on the same file
 without waiting for the callback. For this scenario,
 `fs.createWriteStream` is strongly recommended.