psi: Remove repeated verbose comment

Comment in function psi_task_switch,there are two same lines.
...
* runtime state, the cgroup that contains both tasks
* runtime state, the cgroup that contains both tasks
...

Signed-off-by: Liu Xinpeng <liuxp11@chinatelecom.cn>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Link: https://lore.kernel.org/r/1635133586-84611-1-git-send-email-liuxp11@chinatelecom.cn