Fix analyzer hints and warnings in test/.

test/global/binstubs/outdated_snapshot_test.dart

Index: test/global/binstubs/outdated_snapshot_test.dart
diff --git a/test/global/binstubs/outdated_snapshot_test.dart b/test/global/binstubs/outdated_snapshot_test.dart
index 989619d98dda2267070cf580e7ad4e8428e56e24..52ae928d7bb27626e6fbe5c4aa37216958d6a1c8 100644
--- a/test/global/binstubs/outdated_snapshot_test.dart
+++ b/test/global/binstubs/outdated_snapshot_test.dart
@@ -2,8 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'dart:io';
-
 import 'package:path/path.dart' as p;
 import 'package:pub/src/io.dart';
 import 'package:scheduled_test/scheduled_process.dart';