Remove more tests which depend on dartdoc, which has been deleted.

tools/dom/docs/bin/docs.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.
-
-/**
- * This program reads the HTML libraries from [LIB_PATH] and outputs their
- * documentation to [JSON_PATH].
- */
-
-import 'dart:io';
-import 'dart:async';
-
-import 'package:path/path.dart' as path;
-
-import '../lib/docs.dart';
-
-final String json_path = Platform.script.resolve('../docs.json').toFilePath();
-final String lib_uri = Platform.script.resolve('../../../../sdk').toString();
-
-main() {
-  print('Converting HTML docs from $lib_uri to $json_path.');
-
-  convert(lib_uri, json_path)
-    .then((bool anyErrors) {
-      print('Converted HTML docs ${anyErrors ? "with": "without"}'
-        ' errors.');
-    });
-}