[analyzer] remove "auto-generated do not edit" comments

pkg/analyzer/test/generated/ast_test.dart

Index: pkg/analyzer/test/generated/ast_test.dart
diff --git a/pkg/analyzer/test/generated/ast_test.dart b/pkg/analyzer/test/generated/ast_test.dart
index dbbfe42af0f5d3c7249570f9539f91c0815a9ca8..3da17e2cef8c3678645787debd57749151683cff 100644
--- a/pkg/analyzer/test/generated/ast_test.dart
+++ b/pkg/analyzer/test/generated/ast_test.dart
@@ -2,9 +2,6 @@
 // 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 code was auto-generated, is not intended to be edited, and is subject to
-// significant change. Please see the README file for more information.
-
 library engine.ast_test;
 
 import 'package:analyzer/src/generated/ast.dart';