doc: reword possessive form of Node.js in http.md

Throughout the docs, we sometimes write the possessive of _Node.js_ as
_Node.js'_ and other times as _Node.js's_. The former conforms with some
generally accepted style guides (e.g., Associated Press Stylebook) while
the latter complies with others (e.g., Chicago Manual of Style).

Since there is no clear authoritative answer as to which form is
correct, and since (at least to me) both are visually jarring and
sometimes cause a pause to understand, I'd like to reword things to
eliminate the possessive form where possible.

This is one of those examples.

PR-URL: nodejs#31748
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

doc/api/http.md

@@ -25,7 +25,7 @@ HTTP message headers are represented by an object like this:
 
 Keys are lowercased. Values are not modified.
 
-In order to support the full spectrum of possible HTTP applications, Node.js's
+In order to support the full spectrum of possible HTTP applications, the Node.js
 HTTP API is very low-level. It deals with stream handling and message
 parsing only. It parses a message into headers and body but it does not
 parse the actual headers or the body.