http: remove old, confusing comment

The comment refers to a property (called `_pendings`) that no longer
exists.

PR-URL: https://github.com/nodejs/node/pull/5233
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: James M Snell <jasnell@gmail.com>

lib/_http_incoming.js

@@ -20,10 +20,6 @@ exports.readStop = readStop;
 function IncomingMessage(socket) {
   Stream.Readable.call(this);
 
-  // XXX This implementation is kind of all over the place
-  // When the parser emits body chunks, they go in this list.
-  // _read() pulls them out, and when it finds EOF, it ends.
-
   this.socket = socket;
   this.connection = socket;