Private-equity firm Olympus Partners closed this week on the sale of the world’s largest Pizza Hut franchisee in a deal worth more than $1 billion, according to sources familiar with the transaction. Olympus officials confirmed that they had sold Overland Park, Kan.-based NPC International, which is also a national Wendy’s franchisee, to a private buyer, but declined to identify the latter party. Olympus had bought NPC for approximately $755 million in December 2011. Under Olympus’ ownership, NPC became a Wendy’s franchisee.