Fix Warning

Warning: call_user_func() expects parameter 1 to be a valid callback, class 'PHPSocketIO\Engine\Transports\PollingXHR' does not have a method 'dataRequestOnClose'

src/Engine/Transports/Polling.php

@@ -98,7 +98,7 @@ public function dataRequestCleanup()
         $this->dataReq = $this->dataRes = null;
     }
 
-    public function dataRequestClose()
+    public function dataRequestOnClose()
     {
         $this->dataRequestCleanup();
         $this->onError('data request connection closed prematurely');