Adopt `Sendable` in `ChannelHandlers.swift` (#2144)
Adopt `Sendable` in `ChannelHandlers.swift` (#2144)

Co-authored-by: Cory Benfield <e2b4f0650e369574e9b0029c3b3893634b6d4097@apple.com>
apple/swift-nio,apple/swift-nio,apple/swift-nio,apple/swift-nio,apple/swift-nio