Because you have to be skeptical of everything on April Fools’ Day, we were dubious when we heard whispers that Todd English is planning to close Olives, his flagship restaurant in Charlestown. According to the rumor, which surfaced Monday on Facebook and various food blogs, English is shutting his landmark restaurant, and a Legal Sea Foods Legal Test Kitchen will open in its place. Olives, which English opened over 20 years ago, has unquestionably lost some of its luster in recent years. In 2010, it closed following a grease fire, and the restaurant remained dark for two years. When the glass doors did finally swing back open last year, reviews of the revamped menu were mixed. So what’s he up to? As celebrity chefs go, English is kind of mercurial, always opening or closing something. But we’re told by someone close to him that English is not, in fact, closing Olives. At least not yet.