Remove more libraries directives from server

pkg/analysis_server/lib/src/services/correction/flutter_util.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.
 
-library services.src.correction.flutter_util;
-
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/dart/element/type.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 const _FLUTTER_WIDGET_NAME = "Widget";
 const _FLUTTER_WIDGET_URI = "package:flutter/src/widgets/framework.dart";
 
 void convertFlutterChildToChildren(
     InstanceCreationExpression childArg,
@@ skipping 156 matching lines @@
       orElse: () => null);
   if (superType == null) {
     return false;
   }
   Uri uri = superType.element?.source?.uri;
   if (uri.toString() != _FLUTTER_WIDGET_URI) {
     return false;
   }
   return true;
 }