By Steve Holland WASHINGTON (Reuters) -The private Russian military company, the Wagner Group, took delivery of an arms shipment from North Korea to help bolster Russian forces in Ukraine, a sign of the group’s expanding role in that conflict, the White House said on Thursday. Wagner owner Yevgeny Prigozhin denied the assertion as “gossip and speculation”. John Kirby, spokesperson for the White House National Security Council, said Wagner was searching around the world for arms suppliers to support its military operations in Ukraine. “We can confirm that North Korea has completed an initial ar…