posix-cpu-timers: cpu_clock_sample_group() no longer needs siglock

As of e78c3496 ("time, signal: Protect resource use statistics with
seqlock") cpu_clock_sample_group() no longer needs siglock protection so
remove the stale comment.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lkml.kernel.org/r/87eeuevduq.fsf@x220.int.ebiederm.org

kernel/time/posix-cpu-timers.c

@@ -336,9 +336,7 @@ static void __thread_group_cputime(struct task_struct *tsk, u64 *samples)
 /*
  * Sample a process (thread group) clock for the given task clkid. If the
  * group's cputime accounting is already enabled, read the atomic
- * store. Otherwise a full update is required.  Task's sighand lock must be
- * held to protect the task traversal on a full update. clkid is already
- * validated.
+ * store. Otherwise a full update is required.  clkid is already validated.
  */
 static u64 cpu_clock_sample_group(const clockid_t clkid, struct task_struct *p,
 				  bool start)