Walmart Inc. said on Monday longtime executive Brett Biggs will step down from his role as chief financial officer of the world’s largest retailer next year. Biggs, the finance chief since 2015, helped oversee a period of rapid change at Walmart as the brick-and-mortar retailer launched and expanded a number of initiatives to help fend off competition from Amazon.com Inc. Walmart made its biggest overseas investment in 2018 with a $16 billion deal to buy a majority stake in Indian online marketplace Flipkart, and beefed up its U.S. e-commerce business through the purchase of apparel retailers Modcloth and Bonobos. Monday’s announcement came as a surprise to some analysts who had viewed Biggs as next in line for Walmart’s top job. “Bret Biggs was a candidate to ultimately succeed Doug McMillon as CEO, given his long tenure at the company and broad experience across business units and functions outside of finance,” …