Remove unused imports missed in earlier CL

pkg/analysis_server/lib/src/services/completion/dart/completion_manager.dart

Index: pkg/analysis_server/lib/src/services/completion/dart/completion_manager.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/dart/completion_manager.dart b/pkg/analysis_server/lib/src/services/completion/dart/completion_manager.dart
index f620c83c591e3380f6d93e6225fa73909904d4f9..7cba4580f7e4332c89857da5113aa86607516187 100644
--- a/pkg/analysis_server/lib/src/services/completion/dart/completion_manager.dart
+++ b/pkg/analysis_server/lib/src/services/completion/dart/completion_manager.dart
@@ -29,13 +29,10 @@ import 'package:analysis_server/src/services/completion/dart/type_member_contrib
 import 'package:analysis_server/src/services/completion/dart/uri_contributor.dart';
 import 'package:analysis_server/src/services/completion/dart/variable_name_contributor.dart';
 import 'package:analyzer/dart/ast/ast.dart';
-import 'package:analyzer/dart/ast/standard_ast_factory.dart';
-import 'package:analyzer/dart/ast/token.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/src/dart/analysis/driver.dart';
-import 'package:analyzer/src/dart/ast/token.dart';
 import 'package:analyzer/src/generated/engine.dart' hide AnalysisResult;
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/task/model.dart';