Tango icons are in its own tango.soc palette. No
need to add them to the standard palette.

This reverts commit b9c98414.

Change-Id: Id19d869ce8744cf55e64f4d003b8011f9df0023f
Reviewed-on: https://gerrit.libreoffice.org/3738Reviewed-by: Tor Lillqvist <tml@iki.fi>
Tested-by: Tor Lillqvist <tml@iki.fi>