The city of Boston says a penthouse built by Bob Vila, one of the house renovators from the public-TV series "This Old House," must go. Vila built the penthouse in a condo in Boston's posh Back Bay area eight years ago but never obtained the necessary permits for the work. "He should have known better," said Ann Gleason, chairman of the city's Back Bay Architectural Commission. Cecelia Lehar, who bought the condominium from Vila, is going to court in a bid to save the penthouse. Last week city officials gave her until March 25 to remove it.