China’s market regulator is beginning a probe into a unit of Kuaishou Technology for how live-streaming services are used to promote e-commerce, a potential setback for the popular video service that has been expanding into online sales. The State Administration for Market Regulation is filing a case for an investigation of Chengdu Kuaigou Technology Co. for suspected violations of the country’s e-commerce rules, as well as other laws and regulations, state broadcaster CCTV reported on Friday. C...