Add missing param to constructor

This should fix `15:02:44 Gateway     System.MissingMethodException: Method not found: 'Void WebSocket4Net.WebSocket..ctor(System.String, System.String, System.Collections.Generic.List`1<System.Collections.Generic.KeyValuePair`2<System.String,System.String>>, System.Collections.Generic.List`1<System.Collections.Generic.KeyValuePair`2<System.String,System.String>>, System.String, System.String, WebSocket4Net.WebSocketVersion, System.Net.EndPoint)'.`

src/Discord.Net.Providers.WS4Net/WS4NetClient.cs

@@ -66,7 +66,7 @@ namespace Discord.Net.Providers.WS4Net
             _cancelTokenSource = new CancellationTokenSource();
             _cancelToken = CancellationTokenSource.CreateLinkedTokenSource(_parentToken, _cancelTokenSource.Token).Token;
 
-            _client = new WS4NetSocket(host, customHeaderItems: _headers.ToList())
+            _client = new WS4NetSocket(host, "", customHeaderItems: _headers.ToList())
             {
                 EnableAutoSendPing = false,
                 NoDelay = true,
@@ -163,4 +163,4 @@ namespace Discord.Net.Providers.WS4Net
             Closed(ex).GetAwaiter().GetResult();
         }
     }
-}
+}