By MAYSOON KHAN ALBANY, N.Y. (AP) — New Yorkers under age 21 will be prohibited from buying semiautomatic rifles under a new law signed Monday by Gov. Kathy Hochul, making the state among the first to enact a major gun control initiative following a wave of deadly mass shootings. Hochul, a Democrat, signed 10 public safety-related bills, including one that will require microstamping in new firearms,