fixed phpdocs

lib/Twig/NodeTraverser.php

@@ -55,7 +55,7 @@ class Twig_NodeTraverser
      *
      * @param Twig_Node $node A Twig_Node instance
      *
-     * @return Twig_NodeInterface
+     * @return Twig_Node
      */
     public function traverse(Twig_Node $node)
     {

lib/Twig/NodeVisitor/Optimizer.php

@@ -113,7 +113,7 @@ class Twig_NodeVisitor_Optimizer implements Twig_NodeVisitorInterface
      * @param Twig_Node        $node A Node
      * @param Twig_Environment $env  The current Twig environment
      *
-     * @return Twig_NodeInterface
+     * @return Twig_Node
      */
     protected function optimizeRawFilter(Twig_Node $node, Twig_Environment $env)
     {