Clean up after some recent code changes

pkg/analyzer_plugin/lib/plugin/completion_mixin.dart

 // Copyright (c) 2017, 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.
 
 import 'dart:async';
 
 import 'package:analyzer/dart/analysis/results.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
 import 'package:analyzer_plugin/plugin/plugin.dart';
 import 'package:analyzer_plugin/protocol/protocol.dart';
@@ skipping 46 matching lines @@
  * [AnalysisDriver].
  *
  * Clients may not extend or implement this class, but are allowed to use it as
  * a mix-in when creating a subclass of [ServerPlugin] that also uses
  * [CompletionMixin] as a mix-in.
  */
 abstract class DartCompletionMixin implements CompletionMixin {
   @override
   Future<CompletionRequest> getCompletionRequest(
       CompletionGetSuggestionsParams parameters) async {
-    String path = parameters.file;
     ResolveResult result = await getResolveResult(parameters.file);
     return new DartCompletionRequestImpl(
         resourceProvider, parameters.offset, result);
   }
 }