Pershing Square Capital Management, the activist fund run by billionaire Bill Ackman, sold about a quarter of its stake in Restaurant Brands International Inc. as part of a portfolio rebalancing, according to a person familiar with the matter. Pershing Square sold 10 million shares for $61 apiece, people with knowledge of the details said, asking not to be identified as the details aren’t public. Restaurant Brands shares fell 2.4 percent to $60.65 at 9:49 a.m. The New York-based hedge fund is the largest holder in Oakville, Ontario-based Restaurant Brands, the parent company of Burger King and Tim Hortons, according to...