Remove unittest and matcher from the repo.

pkg/matcher/lib/src/throws_matchers.dart

-// Copyright (c) 2014, 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.
-
-library matcher.throws_matchers;
-
-import 'error_matchers.dart';
-import 'interfaces.dart';
-import 'throws_matcher.dart';
-
-/// A matcher for functions that throw ArgumentError.
-const Matcher throwsArgumentError = const Throws(isArgumentError);
-
-/// A matcher for functions that throw ConcurrentModificationError.
-const Matcher throwsConcurrentModificationError =
-    const Throws(isConcurrentModificationError);
-
-/// A matcher for functions that throw CyclicInitializationError.
-const Matcher throwsCyclicInitializationError =
-    const Throws(isCyclicInitializationError);
-
-/// A matcher for functions that throw Exception.
-const Matcher throwsException = const Throws(isException);
-
-/// A matcher for functions that throw FormatException.
-const Matcher throwsFormatException = const Throws(isFormatException);
-
-/// A matcher for functions that throw NoSuchMethodError.
-const Matcher throwsNoSuchMethodError = const Throws(isNoSuchMethodError);
-
-/// A matcher for functions that throw NullThrownError.
-const Matcher throwsNullThrownError = const Throws(isNullThrownError);
-
-/// A matcher for functions that throw RangeError.
-const Matcher throwsRangeError = const Throws(isRangeError);
-
-/// A matcher for functions that throw StateError.
-const Matcher throwsStateError = const Throws(isStateError);
-
-/// A matcher for functions that throw Exception.
-const Matcher throwsUnimplementedError = const Throws(isUnimplementedError);
-
-/// A matcher for functions that throw UnsupportedError.
-const Matcher throwsUnsupportedError = const Throws(isUnsupportedError);