Bush Twins Get a Little Payback in Prime TimeBy JODI WILGORENPublished: September 1, 2004 aybe girls do just want to have fun. The Bush girls, at least.Forget four years of shunning the spotlight. President Bush's twin 22-year-olds, Jenna and Barbara, strutted into it last night with a sassy, sexy serenade to their parents at the Republican National Convention, every wisecracking word broadcast live on national television. They spared no one."She thinks 'Sex in the City' is something married people do, but never talk about," Jenna, the blonde, razzed her grandmother, Barbara Bush. Jenna was referring to the HBO program "Sex...