remove support for analyzer configuration in pubspec

pkg/analyzer/test/source/config_test.dart

-// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
-// 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 'package:analyzer/source/config.dart';
-import 'package:test/test.dart';
-import 'package:yaml/yaml.dart';
-
-main() {
-  group('Analysis Config', () {
-    test('parseConfigSource', () {
-      String source = r'''
-analyzer:
-  configuration: google/strict
-''';
-      YamlMap options = loadYamlNode(source);
-      AnalysisConfigurationDescriptor descriptor =
-          new AnalysisConfigurationDescriptor.fromAnalyzerOptions(
-              options['analyzer']);
-      expect(descriptor.package, 'google');
-      expect(descriptor.pragma, 'strict');
-    });
-  });
-}