Google’s digital ad sales continued to grow at a healthy clip during the holiday season, but that wasn’t enough to offset investors’ worries about whether its big bet on artificial intelligence will yield as big a jackpot as once envisioned. The October-December results released Tuesday by Google parent Alphabet Inc. showed the company is continuing to reap even more profits from its dominant search engine and other peripheral services. More importantly, revenue growth in the Google Cloud division tethered to the AI craze wasn’t as robust as had been anticipated.