network: Drop any traces of ISDN

This has been removed a long time ago and we should probably spend a
little bit more time on keeping the networking code tidy :)

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

langs/ru/cgi-bin/ru.pl

@@ -906,7 +906,6 @@
 'hour' => 'Час',
 'hours' => 'Часы',
 'hours2' => 'Часы',
-'ibod for dual isdn only' => 'iBOD can only be used with Dual ISDN.',
 'icmp selected but no type' => 'ICMP selected for protocol, but no ICMP type specified.',
 'icmp type' => 'ICMP Type',
 'id' => 'ID',
@@ -1031,10 +1030,6 @@
 'iptmangles' => 'IPTable Mangles',
 'iptnats' => 'IPTable Network Address Translation',
 'ipts' => 'iptables',
-'isdn' => 'ISDN',
-'isdn settings' => 'Additional ISDN settings:',
-'isdn1' => 'Single ISDN',
-'isdn2' => 'Dual ISDN',
 'january' => 'Январь',
 'javascript menu error1' => 'If the drop down menus aren\'t working, disable javascript on the',
 'javascript menu error2' => 'page.',