Doc suggestion: `orderedUpdate()` make `private`

[garvankeeley]

I think making orderedUpdate() private in your final example would be the most realistic usage:

actor Counter {
    private static let data = ["A", "B", "C"]
    private var cursor = 0
    private let queue = SerialQueueThrowing()
    private func orderedUpdate() async {
        cursor += 1
        await Task.yield()
        debugPrint(Self.data[cursor % Self.data.count])
    }
    func update() async throws {
        try await queue.enqueue {
            await self.orderedUpdate()
        }
    }
}