Updated broadcast async to RxPHP 2.0

Author: WyriHaximus

examples/broadcasts-async.php

@@ -11,10 +11,10 @@
 $loop = Factory::create();
 $client = AsyncClient::create($loop, require 'resolve_key.php');
 
-$client->broadcasts()->subscribe(new CallbackObserver(function (BroadcastInterface $broadcast) {
+$client->broadcasts()->subscribe(function (BroadcastInterface $broadcast) {
     resource_pretty_print($broadcast);
 }, function ($e) {
     echo (string)$e;
-}));
+});
 
 $loop->run();