Remove unused 'cur_skey' argument from IndexScanOK()
Commit
a78fcfb51243 removed the last use of it.
Author: Hugo Zhang, Aleksander Alekseev
Reviewed-by: Daniel Gustafsson
Discussion: https://www.postgresql.org/message-id/NT0PR01MB129459E243721B954611938F9CDD2%40NT0PR01MB1294.CHNPR01.prod.partner.outlook.cn