doc: remove ES6/ECMAScript 2015 from buffer.md

As the introduction of ES6 features recedes further into the past, it
is less and less relevant (and more and more distracting) to cite it in
documentation text. Remove mention in buffer.md.

Backport-PR-URL: #21590
PR-URL: #19685
Reviewed-By: Tiancheng "Timothy" Gu <timothygu99@gmail.com>
Reviewed-By: Vse Mozhet Byt <vsemozhetbyt@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

doc/api/buffer.md

@@ -6,8 +6,9 @@
 
 Prior to the introduction of [`TypedArray`], the JavaScript language had no
 mechanism for reading or manipulating streams of binary data. The `Buffer` class
-was introduced as part of the Node.js API to enable interaction with octet
-streams in TCP streams, file system operations, and other contexts.
+was introduced as part of the Node.js API to make it possible to interact with
+octet streams in the context of things like TCP streams and file system
+operations.
 
 With [`TypedArray`] now available, the `Buffer` class implements the
 [`Uint8Array`] API in a manner that is more optimized and suitable for Node.js.