Revert "Implemented strict http request serialization for APIs that forbid a session to be used in concurrent requests (e.g. dedimania)."

This reverts commit b0732bee96.
Solution required PHP 7.0.7, thus breaking requirement of compatibility with PHP 5.4.

core/Files/AsyncHttpRequest.php

@@ -36,7 +36,6 @@ class AsyncHttpRequest implements UsageInformationAble {
 	private $contentType = 'text/xml; charset=UTF-8;';
 	private $timeout     = 60;
 	private $headers     = array();
-	private $serialize   = false;
 
 	public function __construct($maniaControl, $url) {
 		$this->maniaControl = $maniaControl;
@@ -59,7 +58,6 @@ class AsyncHttpRequest implements UsageInformationAble {
 		        ->set(CURLOPT_RETURNTRANSFER, true)//
 		        ->set(CURLOPT_FOLLOWLOCATION, true)// support redirect
 		        ->set(CURLOPT_SSL_VERIFYPEER, false);
-		$request->setSerialize($this->serialize); // serialize requests to this host
 		return $request;
 	}
 
@@ -230,13 +228,4 @@ class AsyncHttpRequest implements UsageInformationAble {
 	public function setTimeout($timeout) {
 		$this->timeout = $timeout;
 	}
-
-	/**
-	 * Sets whether the request to the same host should be serialized.
-	 *
-	 * @param bool $serialize
-	 */
-	public function setSerialize($serialize = true) {
-		$this->serialize = $serialize;
-	}
 }