sched,doc: sched_debug_verbose cmdline should be sched_verbose

The cmdline should include sched_verbose but not sched_debug_verbose
as sched_debug_verbose is only the variant name in code.

Fixes: 9406415f ("sched/debug: Rename the sched_debug parameter to sched_verbose")
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Valentin Schneider <valentin.schneider@arm.com>
Link: https://lkml.kernel.org/r/20210504105344.31344-1-song.bao.hua@hisilicon.com