Online fast-fashion retailer Shein has dropped Brunswick and FGS, two communications firms that were supporting its push for a London initial public offering (IPO), a source familiar with the matter confirmed on Friday, in the latest sign the flotation is not going to plan. Steep tariffs on Chinese goods imposed by U.S. President Donald Trump, along with the removal of a duty exemption on low-value ecommerce packages, are challenging Shein's business model, which relies on shipping clothes from factories in China directly to customers around the world. Brunswick was assisting with media relations while FGS was tasked with government relations,...