Fix analyzer hints and warnings in test/.

test/validator/sdk_constraint_test.dart

Index: test/validator/sdk_constraint_test.dart
diff --git a/test/validator/sdk_constraint_test.dart b/test/validator/sdk_constraint_test.dart
index f2e6303efba963ef70c8e192eca9a00d6e83e6c3..ce09d7110133295432f023d7964a619b55a098cc 100644
--- a/test/validator/sdk_constraint_test.dart
+++ b/test/validator/sdk_constraint_test.dart
@@ -2,12 +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:async';
-import 'dart:convert';
-
-import 'package:http/http.dart' as http;
-import 'package:http/testing.dart';
-import 'package:path/path.dart' as path;
 import 'package:pub/src/entrypoint.dart';
 import 'package:pub/src/validator.dart';
 import 'package:pub/src/validator/sdk_constraint.dart';