[Modify] Polish it

Author: sta

websocket-sharp/WebSocket.cs

@@ -815,8 +815,9 @@ private bool accept ()
 
       lock (_forState) {
         if (_readyState == WebSocketState.Open) {
-          var msg = "The handshake request has already been accepted.";
-          _logger.Warn (msg);
+          var msg = "The connection has already been established.";
+
+          _logger.Trace (msg);
 
           return false;
         }