BON JOVI WEEK ''The second it was announced we were doing a Bon Jovi week, [Jordin] requested her song early. She knew exactly what she was going to sing,'' Idol's music guru Michael Orland told EW. Perhaps she shouldn't have been so rash in going with the dude-rock ''Livin' on a Prayer'': Weighed down by a scary-big mop of red-streaked hair (''like something out of The Addams Family,'' Simon carped), Jordin looked utterly unconvincing stomping about and sidling up to her accompanying guitarists. And the singing? ''Terrible,'' Simon said. Her worst moment of the season by far.