docs: scheduler: Update new path for the sysctl knobs

Add missing update for the documentation bit of some scheduler knob.
The knobs have been moved to /debug/sched/ location (with adjusted names).

Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Reviewed-by: Alex Shi <alexs@kernel.org>
Tested-by: Yanteng Si <siyanteng@loongson.cn>
Link: https://lore.kernel.org/r/20220816121907.841-1-lukasz.luba@arm.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>