block: correct stale comment in rq_qos_wait

The rq_qos_wait calls common wake-up function rq_qos_wake_function to get
token. Just replace stale wbt_wake_function with rq_qos_wake_function in
comment.

Signed-off-by: Kemeng Shi <shikemeng@huaweicloud.com>
Acked-by: Tejun Heo <tj@kernel.org>
Link: https://lore.kernel.org/r/20230914091508.36232-1-shikemeng@huaweicloud.com


Signed-off-by: Jens Axboe <axboe@kernel.dk>