STOCKHOLM (Reuters) – Sweden’s prime minister threatened on Thursday to step down just three months before a general election is due, if the centre-right opposition succeeds in winning a vote of no-confidence against the interior minister over his handling of gang crime. The Moderates, the Liberals and the Christian Democrats parties said they would support a no-confidence vote planned for next week against Justice and Interior minister Morgan Johansson called by the populist Sweden Democrats party. They say Johansson should take responsibility for failing to tackle gang crime that has led to …