removed unsused translation file

lib/plugins/info/lang/sl/lang.php

-<?php
-/**
- * English language file
- *
- * @license    GPL 2 (http://www.gnu.org/licenses/gpl.html)
- * @author     Guillaume Turri <guillaume.turri@gmail.com>
- */
- 
-$lang['encoding']              = 'utf-8';
-$lang['direction']             = 'ltr';
-$lang['onHidden']              = 'Click to display ⇲';
-$lang['onVisible']             = 'Click to hide ⇱';