Bob van Dijk, CEO of e-commerce group Naspers, poses for a photograph in front of the company logo after holding a media briefing in Johannesburg, South Africa, October 9, 2019. REUTERS/Siphiwe Sibeko/File photo Acquire Licensing Rights JOHANNESBURG, Sept 18 (Reuters) - Dutch-listed technology investor Prosus NV (PRX.AS) and its South African parent Naspers (NPNJn.J) said on Monday Bob van Dijk has stepped down as chief executive officer from both companies. The companies named investment chief Ervin Tu, a previous VisionBank manager and Goldman Sachs technology banker, as interim CEO. The companies did not provide a reason for Van Dijk's departure....