kconfig/gconf: kill deadcode

The only call site of renderer_toggled() has been commented out since Apr. 2003,
as per Linus' Linux history repository:

 commit e7f67eb3c0570aa50c1cc0707b478a6d93bdc255
 Author: Roman Zippel <zippel@linux-m68k.org>
 Date:   Fri Apr 4 04:18:05 2003 -0800

    [PATCH] gconf update

    A gconf update by Romain Li<C3><A9>vin <roms@tilp.info>
    - fixed bug when double-clicking for changing value.
    - expand row when enabling a row with a submenu.
    - various bug fixes

As this result in a warning:

scripts/kconfig/gconf.c:891:13: warning: 'renderer_toggled' defined but not used

just nuke that code.

Signed-off-by: Arnaud Lacombe <lacombar@gmail.com>