By Jeffrey Dastin and Akash Sriram (Reuters) -Alphabet disappointed Wall Street on Tuesday as holiday season advertising sales came in below expectations and the company said its spending on data centers to support its artificial intelligence plans would jump this year. Shares fell 6% in after-hours trade. Alphabet has faced tough competition for ad budgets from other online platforms such as Facebook, Instagram, TikTok and Amazon.com, and economic signals in the U.S. have been mixed. Ad revenue in the fourth quarter was $65.5 billion, up from $59.0 billion in the year ago quarter but short of…