By Alun John and Naomi Rovnick LONDON (Reuters) -Just months after a U.S. tariff shock whacked the dollar, a rush by overseas investors to protect U.S. holdings from the sliding currency has slowed sharply - a vote of confidence that's helping the greenback recover from its worst rout in years. While analysts say investor hedging is higher than ​it has been historically, such activity has slowed from the period immediately after the April 2 "Liberation Day", when U.S. President Donald Trump announced swe ...