remove redundant import

Author: eEQK

pkgs/_test_macros/lib/built_value.dart

@@ -3,7 +3,6 @@
 // BSD-style license that can be found in the LICENSE file.
 
 import 'dart:async';
-import 'dart:io';
 
 import 'package:dart_model/dart_model.dart';
 // ignore: implementation_imports

pkgs/dart_model/lib/src/json_buffer/json_buffer_builder.dart

@@ -4,7 +4,6 @@
 
 import 'dart:collection';
 import 'dart:convert';
-import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:convert/convert.dart';