Update libraries/joomla/document/json/json.php

Allow the document to be cached if required.

libraries/joomla/document/json/json.php

@@ -57,7 +57,7 @@ public function __construct($options = array())
 	 */
 	public function render($cache = false, $params = array())
 	{
-		JResponse::allowCache(false);
+		JResponse::allowCache($cache);
 		JResponse::setHeader('Content-disposition', 'attachment; filename="' . $this->getName() . '.json"', true);
 
 		parent::render();