sched/header: Remove leftover, obsolete comment

There is no more set_task_vxid() helper, remove its description.
Signed-off-by: Perr Zhang <strongbox8@zoho.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20170602035953.28949-1-strongbox8@zoho.comSigned-off-by: Ingo Molnar <mingo@kernel.org>

include/linux/sched.h

@@ -1096,8 +1096,6 @@ static inline struct pid *task_session(struct task_struct *task)
  *                     current.
  * task_xid_nr_ns()  : id seen from the ns specified;
  *
- * set_task_vxid()   : assigns a virtual id to a task;
- *
  * see also pid_nr() etc in include/linux/pid.h
  */
 pid_t __task_pid_nr_ns(struct task_struct *task, enum pid_type type, struct pid_namespace *ns);