feat: remove unused import

Author: Tienisto

rhttp/lib/src/request.dart

@@ -3,7 +3,6 @@ import 'dart:convert';
 
 import 'package:flutter/foundation.dart';
 import 'package:flutter_rust_bridge/flutter_rust_bridge.dart';
-import 'package:meta/meta.dart';
 import 'package:rhttp/src/dev_tools.dart';
 import 'package:rhttp/src/interceptor/interceptor.dart';
 import 'package:rhttp/src/model/exception.dart';