test rename overhaul: step 8 - language tests

tests/language/src/DuplicateImplementsTest.dart

-// Copyright (c) 2012, 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.
-// Check that duplicate types in implements/extends list are
-// compile-time errors.
-
-interface I { }
-interface J { }
-interface K<T> { }
-
-class X implements I, J, I { }               /// 01: compile-time error
-class X implements J, I, K<int>, K<int> { }  /// 02: compile-time error
-
-interface Z extends I, J, J { }              /// 03: compile-time error
-interface Z extends K<int>, K<int> { }       /// 04: compile-time error
-
-main() {
-  return null;
-}