fix: 修复flutter编译失败

webrtc_controller_flutter/lib/controller/remote_controller.dart

@@ -14,8 +14,8 @@ class RemoteController {
   final String serverUrl;
   final String deviceId;
   final String targetDeviceId;
-  final String? authType;
-  final String? authValue;
+  String? authType;
+  String? authValue;
 
   late final SignalingClient _signaling;
   WebRtcController? _webRtc;