Nike's grip on China's sneaker market is slipping. Once a status symbol among Chinese consumers, analysts say it's increasingly losing cultural relevance even as its products remain innovative.The sportswear giant's stock tumbled by 9% in early trading on Friday after reporting its Q2 fiscal results on Thursday. While sales in North America rose 9% to $5.63 billion during the quarter, sales in Greater China were down 17$1.42 billion — falling short of Wall Street's expectations.Nike CEO Elliott Hill ...