rcu-tasks: Fix the comments for tasks_rcu_exit_srcu_stall_timer

The synchronize_srcu() has been removed by commit("rcu-tasks: Eliminate
deadlocks involving do_exit() and RCU tasks") in rcu_tasks_postscan.
This commit therefore fixes the tasks_rcu_exit_srcu_stall_timer comment.
Signed-off-by: Zqiang <qiang.zhang1211@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

kernel/rcu/tasks.h

@@ -150,7 +150,7 @@ static struct rcu_tasks rt_name =							\
 
 #ifdef CONFIG_TASKS_RCU
 
-/* Report delay in synchronize_srcu() completion in rcu_tasks_postscan(). */
+/* Report delay of scan exiting tasklist in rcu_tasks_postscan(). */
 static void tasks_rcu_exit_srcu_stall(struct timer_list *unused);
 static DEFINE_TIMER(tasks_rcu_exit_srcu_stall_timer, tasks_rcu_exit_srcu_stall);
 #endif