Remove kde4/tde/open-url.sh and have LO just use xdg-open.
It's available on TDE builds as well as any recent KDE.  We recently
did this just for gnome-open-url and have had no reported issues.

Change-Id: I4e1ee6caef368051af92023fa382b6fed9d9397e
Reviewed-on: https://gerrit.libreoffice.org/21173Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Michael Stahl <mstahl@redhat.com>
Reviewed-by: Jan-Marek Glogowski <glogow@fbihome.de>