By Stephen Culp NEW YORK (Reuters) -U.S. stocks closed modestly lower on Friday, the last trading day of 2023, capping a robust year-end rally as investors eyed easier monetary policy in the year ahead. The stock market has seen remarkable upward momentum in the closing months of the year, powering all three major indexes to monthly, quarterly and annual gains. For the year, all three posted double-digit growth. “On January of this year, 363 days ago, if I said I think the S&P is going to gain more than 20% in 2023, you would have put me into the slightly nutty category,” said Oliver Pursche, …