cgroup: remove obsolete comment above struct cgroupstats

There's no flag in the delay accounting structure indicates that the task
is waiting on IO since commit 1193829da1a6 ("delayacct: cleanup flags in
struct task_delay_info and functions use it"). So remove the comment.

Signed-off-by: Miaohe Lin <[e-mail]>
Signed-off-by: Tejun Heo <[e-mail]>

include/uapi/linux/cgroupstats.h

···
  * basis. This data is shared using taskstats.
  *
  * Most of these states are derived by looking at the task->state value
- * For the nr_io_wait state, a flag in the delay accounting structure
- * indicates that the task is waiting on IO
  *
  * Each member is aligned to a 8 byte boundary.
  */