Revert "Made the websocket public"

This reverts commit 50d8f27.
We already have the connect() and disconnect() methods.

Sources/ApolloWebSocket/WebSocketTransport.swift

@@ -28,9 +28,8 @@ public class WebSocketTransport {
   public weak var delegate: WebSocketTransportDelegate?
 
   let reconnect: Atomic<Bool>
-  public private(set) var websocket: ApolloWebSocketClient
+  var websocket: ApolloWebSocketClient
   let error: Atomic<Error?> = Atomic(nil)
-
   let serializationFormat = JSONSerializationFormat.self
   private let requestCreator: RequestCreator