Rewrite the negative try-catch tests into a single multi test.

tests/language/src/TryCatch6NegativeTest.dart

-// Copyright (c) 2011, 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.
-// Dart test program for testing try/catch statement without any exceptions
-// being thrown.
-// Negative test should fail compilation, illegal throw specifier.
-
-class Helper {
-  static int f1(int i) {
-    try {
-      int j;
-      j = 10;
-      throw;  // An exception object is needed here.
-    } catch (var e) {
-      i = 200;
-    }
-    return i;
-  }
-}
-
-main() {
-  Expect.equals(1, Helper.f1(1));
-}