Update translation for ovpnmain.cgi

Update translation for ovpnmain.cgi

Hi All,

since the last update made changes for the webinterface of OpenVPN, it's
time to remove unused translations and update the remaining ones for
downloading the client configuration.

Starting here with the German translation.

Best regards

Peer Dietzmann

  'dmz pinhole configuration' => 'Einstellungen des DMZ-Schlupfloches',
  'dmz pinhole rule added' => 'Regel für DMZ-Schlupfloch hinzugefügt;
Starte DMZ-Schlupfloch neu',

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