ZF-6934: fix docblock to show correct return type

git-svn-id: http://framework.zend.com/svn/framework/standard/trunk@15924 44c647ce-9c0f-0410-b52a-842ac1e357ba

library/Zend/Form.php

@@ -1784,7 +1784,7 @@ class Zend_Form implements Iterator, Countable, Zend_Validate_Interface
      * Return a display group
      * 
      * @param  string $name 
-     * @return array|null
+     * @return Zend_Form_DisplayGroup|null
      */
     public function getDisplayGroup($name)
     {