docs: Rename default-configs to configs

docs: Rename default-configs to configs

This was missed at the time.

Fixes: 812b31d3f91 ("configs: rename default-configs to configs and reorganise")
Signed-off-by: Greg Kurz <groug@kaod.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250306174113.427116-1-groug@kaod.org>
Signed-off-by: Thomas Huth <thuth@redhat.com>
(cherry picked from commit 48170c2d865a5937092b1384421b01cd38113042)
(Mjt: context fix in docs/devel/kconfig.rst)
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>