By Piya Sinha-Roy LOS ANGELES (Reuters) – The doors of Dunder Mifflin’s Scranton branch closed for the last time on Thursday as NBC’s “The Office” wrapped up after a nine-season run with a nostalgic finale featuring a long-awaited wedding and the return of the show’s biggest star, Steve Carell. Emmy-winning mockumentary “The Office,” adapted from Ricky Gervais’ British series of the same name, saw a documentary crew filming the daily lives of employees at the Dunder Mifflin paper company, led for several years by hapless boss Michael Scott, played by Carell. …