doc: fix typo in stream doc

Use the plural instead of the possessive for developers

PR-URL: nodejs/node#11560
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Timothy Gu <timothygu99@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

doc/api/stream.md

@@ -21,7 +21,7 @@ const stream = require('stream');
 
 While it is important for all Node.js users to understand how streams work,
 the `stream` module itself is most useful for developers that are creating new
-types of stream instances. Developer's who are primarily *consuming* stream
+types of stream instances. Developers who are primarily *consuming* stream
 objects will rarely (if ever) have need to use the `stream` module directly.
 
 ## Organization of this Document