NEW YORK—A former partner at the McKinsey consulting firm pleaded guilty to insider trading ahead of Goldman Sachs Group Inc’s agreement to buy fintech lender GreenSky Inc for $2.24 billion, U.S. prosecutors said on Wednesday. Puneet Dikshit, 40, pleaded guilty to one count of securities fraud. He was charged last month for allegedly generating about $450,000 said of profit from 2,500 GreenSky call options that he bought in the two days before the merger was announced on Sept. 15. Dikshit now awaits sentencing, Damian Williams, the U.S. Attorney for the Southern District of New York, said in a statement. Authorities said Dikshit led McKinsey’s unsecured lending practice in North America and had been a lead partner advising Goldman. GreenSky is a specialty lender that arranges consumer loans for large one-time purchases. Its share price rose 53 percent on the day the merger was announced. Prosecutors said Dikshit bought his call …