Fix SwiftNetworkConnectionTests build

Author: tfpauly

Sources/SwiftNetwork/Connection/Connection.swift

@@ -990,7 +990,7 @@ public struct DatagramBridge: DatagramProtocol, Sendable {
 #if !NETWORK_EMBEDDED
 @_spi(Essentials)
 @available(Network 0.1.0, *)
-public struct StreamBridge: StreamProtocol {
+public struct StreamBridge: StreamProtocol, Sendable {
     public typealias ContentType = Void
 
     public let belowProtocol: Void
@@ -1010,8 +1010,8 @@ public struct StreamBridge: StreamProtocol {
 
 @_spi(Essentials)
 @available(Network 0.1.0, *)
-public struct NoTransport: StreamProtocol {
-    public enum BelowProtocol {
+public struct NoTransport: StreamProtocol, Sendable {
+    public enum BelowProtocol: Sendable {
         case void
         #if !NETWORK_EMBEDDED
         case bridge(StreamBridge)
@@ -1331,7 +1331,7 @@ public struct QUIC: MultiplexProtocol {
 /// > Note: This type is not intended to be inserted into the protocol stack manually; it is vended by connections that use QUIC.
 @_spi(Essentials)
 @available(Network 0.1.0, *)
-public struct QUICStream: StreamProtocol {
+public struct QUICStream: StreamProtocol, Sendable {
     public let belowProtocol: Void
 
     public enum Directionality: Equatable {