Revert "Use UTF-8 in Thunderbird"

This reverts commit dcdd5c5c01.

root/usr/share/mozilla-mcd/thunderbird.php

@@ -183,11 +183,6 @@ $id++;
 <?php echo $pref;?>("mailnews.start_page_override.mstone", "ignore");
 <?php echo $pref;?>("mail.rights.version", 1);
 
-// Use UTF-8
-<?php echo $pref;?>("font.language.group", "x-unicode");
-<?php echo $pref;?>("mailnews.send_default_charset", "UTF-8");
-<?php echo $pref;?>("mailnews.view_default_charset", "UTF-8");
-
 <?php
 // Include other conf fragment if they exist
 if (is_array(glob("thunderbird.mod.*.php"))){