doc: remove outdated remarks about highWaterMark in fs

`Readable`'s `highWaterMark` has in fact been 64KiB since #52037.

PR-URL: #55462
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/fs.md

@@ -270,9 +270,6 @@ added: v16.11.0
   * `signal` {AbortSignal|undefined} **Default:** `undefined`
 * Returns: {fs.ReadStream}
 
-Unlike the 16 KiB default `highWaterMark` for a {stream.Readable}, the stream
-returned by this method has a default `highWaterMark` of 64 KiB.
-
 `options` can include `start` and `end` values to read a range of bytes from
 the file instead of the entire file. Both `start` and `end` are inclusive and
 start counting at 0, allowed values are in the
@@ -2551,9 +2548,6 @@ changes:
   * `signal` {AbortSignal|null} **Default:** `null`
 * Returns: {fs.ReadStream}
 
-Unlike the 16 KiB default `highWaterMark` for a {stream.Readable}, the stream
-returned by this method has a default `highWaterMark` of 64 KiB.
-
 `options` can include `start` and `end` values to read a range of bytes from
 the file instead of the entire file. Both `start` and `end` are inclusive and
 start counting at 0, allowed values are in the