Instacart Inc. on late Thursday cut its valuation by nearly 40 percent to about $24 billion due to recent market turbulence, in an unusual move that shows how public market volatility affects high-flying private companies. The new valuation marks a substantial drop from last March, when the grocery delivery firm was valued at $39 billion in a $265 million funding round from existing investors including Andreessen Horowitz and Sequoia Capital, as doorstep delivery boomed amid the coronavirus pandemic. Several public companies in the delivery space, including DoorDash Inc., have seen their shares plummet in the past three months amid a broader tech selloff, and as investors worry about growth potential. “We are not immune to the market turbulence that has impacted leading technology companies—both public and private,” said an Instacart spokesperson. The company said the updated valuation would help it attract and retain talent in a tight U.S. labor market …