[presubmit] Enable readability/namespace linter checking.

src/json-stringifier.h

 // Copyright 2012 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_JSON_STRINGIFIER_H_
 #define V8_JSON_STRINGIFIER_H_
 
 #include "src/conversions.h"
 #include "src/lookup.h"
 #include "src/messages.h"
@@ skipping 657 matching lines @@
     }
   } else {
     if (object->IsOneByteRepresentationUnderneath()) {
       SerializeString_<uint8_t, uc16>(object);
     } else {
       SerializeString_<uc16, uc16>(object);
     }
   }
 }
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_JSON_STRINGIFIER_H_