SYDNEY (Reuters) - New Zealand Prime Minister Jacinda Ardern on Monday named finance minister Grant Robertson as deputy prime minister in her new government after Labour Party deputy leader Kelvin Davis ruled himself out from standing. Robertson, who will continue as finance minister, will replace Winston Peters of Labour’s previous coalition partner New Zealand First, while Ardern said Davis wanted to focus on making a difference for the country’s Maori people. A thumping election win gave Ardern the freedom to form the first single-party government since New Zealand adopted a German-style proportional voting system in 1996.