exit: Fix typo in comment: s/sub-theads/sub-threads

Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/exit.c

@@ -1051,7 +1051,7 @@ static int wait_task_zombie(struct wait_opts *wo, struct task_struct *p)
 		 * p->signal fields because the whole thread group is dead
 		 * and nobody can change them.
 		 *
-		 * psig->stats_lock also protects us from our sub-theads
+		 * psig->stats_lock also protects us from our sub-threads
 		 * which can reap other children at the same time. Until
 		 * we change k_getrusage()-like users to rely on this lock
 		 * we have to take ->siglock as well.