futex: Fix outdated comment in struct restart_block

Since commit 2070887 ("futex: fix restart in wait_requeue_pi"),
futex_wait_requeue_pi() no longer uses restart_block. Update the comment
accordingly.

Signed-off-by: Nam Cao <namcao@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250428193445.4571-1-namcao@linutronix.de

Author: covanam

include/linux/restart_block.h

@@ -26,7 +26,7 @@ struct restart_block {
 	unsigned long arch_data;
 	long (*fn)(struct restart_block *);
 	union {
-		/* For futex_wait and futex_wait_requeue_pi */
+		/* For futex_wait() */
 		struct {
 			u32 __user *uaddr;
 			u32 val;