Kansas City Chiefs star (and Taylor Swift’s fiancé) Travis Kelce is getting into the activist investing business. The NFL athlete, podcast host and burgeoning actor joined the activist investment firm Jana Partners in a bid to seek an overhaul of Six Flags, the theme park company that owns Knott’s Berry Farm, Cedar Point and Six Flags amusement parks across the country. Jana disclosed that it now holds approximately 9 percent of Six Flags shares, alongside Kelce, former Gap CEO Glenn Murphy and tech executive and former J.D. Power CEO Dave Habiger. The firm says it plans “to engage with the...