NEW YORK — Pamela Hayden, the longtime voice actor behind Milhouse Van Houten — Bart Simpson’s very uncool friend — is stepping away after 35 years of whining. Hayden, 70, who voiced Milhouse, Jimbo Jones, Rod Flanders, Janey and Malibu Stacy, will sign off from “The Simpsons” on Nov. 24 in a “Treehouse of Horror” episode. “It’s been an honor and a joy to have worked on such a funny, witty, and groundbreaking show,” Hayden said in a statement. “Pamela gave us tons of laughs with Milhouse, the hapless kid with the biggest nose in Springfield.