switch removeFirst to dropFirst
switch removeFirst to dropFirst

we don't need a mutable copy of `array` to alter it, instead we can just drop the first element
tkester/swift-algorithm-club,raywenderlich/swift-algorithm-club,raywenderlich/swift-algorithm-club,TheIronBorn/swift-algorithm-club,tomtclai/swift-algorithm-club,jawwad/swift-algorithm-club,jawwad/swift-algorithm-club,jawwad/swift-algorithm-club,tomtclai/swift-algorithm-club,hollance/swift-algorithm-club,raywenderlich/swift-algorithm-club,TheIronBorn/swift-algorithm-club,tkester/swift-algorithm-club,eugenepavlyuk/swift-algorithm-club,eugenepavlyuk/swift-algorithm-club