docs/sp_SP: Add translation for scheduler/sched-design-CFS.rst

Translate Documentation/scheduler/sched-design-CFS.rst into Spanish

Signed-off-by: Sergio González Collado <sergio.collado@gmail.com>
Reviewed-by: Carlos Bilbao <carlos.bilbao.osdev@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20240707195047.14359-1-sergio.collado@gmail.com