[presubmit] Enable readability/namespace linter checking.

src/regexp/regexp-stack.h

 // Copyright 2009 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.
 
 #ifndef V8_REGEXP_REGEXP_STACK_H_
 #define V8_REGEXP_REGEXP_STACK_H_
 
 #include "src/base/logging.h"
 #include "src/base/macros.h"
 #include "src/globals.h"
@@ skipping 106 matching lines @@
   ThreadLocal thread_local_;
   Isolate* isolate_;
 
   friend class ExternalReference;
   friend class Isolate;
   friend class RegExpStackScope;
 
   DISALLOW_COPY_AND_ASSIGN(RegExpStack);
 };
 
-}}  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_REGEXP_REGEXP_STACK_H_