[SE-0255] Update status to implemented (Swift 5.1)
[SE-0255] Update status to implemented (Swift 5.1)

<https://github.com/apple/swift/pull/24327>
apple/swift-evolution,Nirma/swift-evolution,ddunbar/swift-evolution,abertelrud/swift-evolution,Nirma/swift-evolution,hartbit/swift-evolution,anandabits/swift-evolution,hartbit/swift-evolution,apple/swift-evolution,ddunbar/swift-evolution,natecook1000/swift-evolution,DevAndArtist/swift-evolution,DevAndArtist/swift-evolution,abertelrud/swift-evolution,natecook1000/swift-evolution,anandabits/swift-evolution