Companies in China are cutting back on digital-ad spending as the economy slows and recurring Covid-19 outbreaks weigh on consumption, another sign of waning business confidence in the world’s most populous nation. Chinese internet giants that operate several of the country’s biggest online-advertising platforms recently warned of weak ad spending by their customers in the second quarter. Some also suggested it could be a while before a recovery takes hold, signaling pessimism about the broader economic outlook.