Fix: move class to class directory

htdocs/admin/modules.php

@@ -30,6 +30,7 @@ require("../main.inc.php");
 require_once(DOL_DOCUMENT_ROOT."/lib/admin.lib.php");
 
 $langs->load("errors");
+$langs->load("admin");
 
 $mode=isset($_GET["mode"])?$_GET["mode"]:(isset($_SESSION['mode'])?$_SESSION['mode']:0);
 $mesg=isset($_GET["mesg"])?$_GET["mesg"]:"";