Investors in the Deutsche X-trackers Harvest CSI 300 China A-Shares ETF are enduring the widest price swings on record and have pulled more than $274 million from the fund’s assets in the past four weeks as the government implemented unprecedented intervention measures to stem a rout that wiped out $4 trillion in market value. Historical 30-day volatility in the ETF surged to 96.75 percent on Thursday as the funddropped 3 percent to $39.83 in New York…