Remove more libraries directives from server

pkg/analysis_server/lib/src/provisional/completion/completion.dart

 // Copyright (c) 2015, 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.
 
 /**
  * Support for client code that extends the analysis server by adding new code
  * completion contributors.
  *
  * Plugins can register completion contributor factories.
  * The registered contributor factories will be used to instantiate new
  * contributors to get completions any time a client issues
  * a 'completion.getSuggestions' request.
  *
  * If a plugin wants to add completions, it should implement
  * [CompletionContributorFactory] by including code
  * like the following in the plugin's registerExtensions method:
  *
  *     @override
  *     void registerExtensions(RegisterExtension registerExtension) {
  *       ...
  *       registerExtension(
  *           COMPLETION_CONTRIBUTOR_EXTENSION_POINT_ID,
  *           () => new MyCompletionContributor());
  *       ...
  *     }
  */
-library analysis_server.src.provisional.completion.core;
-
 import 'package:analysis_server/src/plugin/server_plugin.dart';
 import 'package:plugin/plugin.dart';
 
 /**
  * The identifier of the extension point that allows plugins to register code
  * completion contributors. The object used as an extension must be a
  * [CompletionContributorFactory].
  */
 final String COMPLETION_CONTRIBUTOR_EXTENSION_POINT_ID = Plugin.join(
     ServerPlugin.UNIQUE_IDENTIFIER,
     ServerPlugin.COMPLETION_CONTRIBUTOR_EXTENSION_POINT);