[debug] remove outdated regression test.

TBR=jgruber@chromium.org
NOTREECHECKS=true
NOTRY=true

Change-Id: Id5d81f863fa6d14ac86d49b6516e577c2da7a999
Reviewed-on: https://chromium-review.googlesource.com/936543Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#51557}

test/mjsunit/mjsunit.status

@@ -160,7 +160,6 @@
   'regress/regress-605470': [PASS, SLOW],
   'regress/regress-655573': [PASS, SLOW],
   'regress/regress-1200351': [PASS, SLOW],
-  'regress/regress-crbug-474297': [PASS, ['gc_stress == False', SKIP]],
   'wasm/embenchen/*': [PASS, SLOW],
   'wasm/unreachable-validation': [PASS, SLOW],
 

test/mjsunit/regress/regress-crbug-474297.js

-// Copyright 2015 the V8 project authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Flags: --gc-interval=33 --expose-gc --allow-natives-syntax
-
-var Debug = %GetDebugContext().Debug;
-Debug.setListener(function(){});
-
-%DebugGetLoadedScripts();
-
-Debug.setListener(null);