Nvidia’s (NVDA-Q) much-awaited results - seen as a barometer of AI chip demand - on Wednesday could prove to be an inflection point for artificial intelligence stocks as technology companies tighten data center spending. Investors have raked in big returns over the last few years from the AI boom that has accrued largely to the so-called “Magnificent Seven”, a group of tech giants that includes Nvidia, Microsoft (MSFT-Q) and automaker Tesla (TSLA-Q). That rally marched on despite growing wariness of the stocks’ high valuations - and whether the billions of dollars in investment would yield significant returns. Those concerns have...