include/block.h: remove outdated comment

There are a couple of errors in bdrv_drained_begin header comment:
- block_job_pause does not exist anymore, it has been replaced
  with job_pause in b15de82867
- job_pause is automatically invoked as a .drained_begin callback
  (child_job_drained_begin) by the child_job BdrvChildClass struct
  in blockjob.c. So no additional pause should be required.

Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Message-Id: <20210903113800.59970-1-eesposit@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

include/block/block.h

@@ -751,9 +751,7 @@ bool bdrv_drain_poll(BlockDriverState *bs, bool recursive,
  * bdrv_drained_begin:
  *
  * Begin a quiesced section for exclusive access to the BDS, by disabling
- * external request sources including NBD server and device model. Note that
- * this doesn't block timers or coroutines from submitting more requests, which
- * means block_job_pause is still necessary.
+ * external request sources including NBD server, block jobs, and device model.
  *
  * This function can be recursive.
  */