Remove useless reference operator.

lib/Cake/Utility/File.php

@@ -530,7 +530,7 @@ class File {
  * @return Folder Current folder
  * @link http://book.cakephp.org/2.0/en/core-utility-libraries/file-folder.html#File::Folder
  */
-	public function &folder() {
+	public function folder() {
 		return $this->Folder;
 	}