NEW YORK (Reuters) -The artificial intelligence theme that has propelled markets over the past couple years faces a crucial moment on Wednesday, when bellwether Nvidia Corp reports its second-quarter results. The declines have taken some of the steam out of an array of tech and other stocks that have sizzled since chatbot ChatGPT unleashed a frenzy over the potential for AI about three years ago. An equal-weighted basket of 50 AI-related stocks tracked by Bespoke Investment Group — which includes many of the world’s biggest tech companies — has soared nearly 170% since the end of 2022, as of Monday.