doc: add missing word in readable.read() text

This adds a missing _is_ in the readable.read() text and makes
small style adjustments.

PR-URL: #41524
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Darshan Sen <raisinten@gmail.com>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

Author: Trott

doc/api/stream.md

@@ -1211,9 +1211,9 @@ added: v0.9.4
 * `size` {number} Optional argument to specify how much data to read.
 * Returns: {string|Buffer|null|any}
 
-The `readable.read()` method pulls some data out of the internal buffer and
-returns it. If no data available to be read, `null` is returned. By default,
-the data will be returned as a `Buffer` object unless an encoding has been
+The `readable.read()` method reads data out of the internal buffer and
+returns it. If no data is available to be read, `null` is returned. By default,
+the data is returned as a `Buffer` object unless an encoding has been
 specified using the `readable.setEncoding()` method or the stream is operating
 in object mode.