[DependencyInjection] fixes typo in triggered deprecation notice.

Author: Hugo Hamon

SimpleXMLElement.php

@@ -11,7 +11,7 @@
 
 namespace Symfony\Component\DependencyInjection;
 
-@trigger_error('The '.__NAMESPACE__.'\SimpleXMLElement method is deprecated since version 2.5 and will be removed in 3.0.', E_USER_DEPRECATED);
+@trigger_error('The '.__NAMESPACE__.'\SimpleXMLElement class is deprecated since version 2.5 and will be removed in 3.0.', E_USER_DEPRECATED);
 
 use Symfony\Component\Config\Util\XmlUtils;
 use Symfony\Component\ExpressionLanguage\Expression;