A month ago, money managers were the most optimistic on gold this year. Now, they can’t seem to unload bullion fast enough. Hedge funds’ net-long positions, or the difference between bets on a price increase and wagers on a decline, fell last week by more than half, the biggest reduction since 2015. Exchange-traded products backed by precious metals saw cash outflows over the past month, while most other commodity funds took in more investor money. Total assets in SPDR Gold Shares, the world’s top bullion ETF, fell to the lowest since March last week. Even with signs of escalating geopolitical tensions...