rcu: Remove stale comment in tree.c

This commit removes a stale comment in rcu/tree.c which was left
out when some code was moved around previously in commit 2036d94a7b
("rcu:  Rework detection of use of RCU by offline CPUs") For reference,
the following updated comment exists a few lines below this which means
the same:

/* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

kernel/rcu/tree.c

@@ -2220,8 +2220,6 @@ static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
 	/* Adjust any no-longer-needed kthreads. */
 	rcu_boost_kthread_setaffinity(rnp, -1);
 
-	/* Remove the dead CPU from the bitmasks in the rcu_node hierarchy. */
-
 	/* Exclude any attempts to start a new grace period. */
 	mutex_lock(&rsp->onoff_mutex);
 	raw_spin_lock_irqsave(&rsp->orphan_lock, flags);