Synchronize this proposal with the language steering group's amendment for the Swift 6 language mode, as [announced](https://forums.swift.org/t/amendment-se-0192-handling-future-enum-cases/68321) and [implemented for Swift 6.0](https://github.com/apple/swift/pull/73481).

[RAMADAN1900]

Synchronize this proposal with the language steering group's amendment for the Swift 6 language mode, as announced and implemented for Swift 6.0.

Originally posted by @xwu in https://github.com/apple/swift-evolution/pull/2450