[presubmit] Enable readability/namespace linter checking.

src/builtins.h

 // Copyright 2011 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_BUILTINS_H_
 #define V8_BUILTINS_H_
 
 #include "src/handles.h"
 
 namespace v8 {
@@ skipping 308 matching lines @@
   static void InitBuiltinFunctionTable();
 
   bool initialized_;
 
   friend class BuiltinFunctionTable;
   friend class Isolate;
 
   DISALLOW_COPY_AND_ASSIGN(Builtins);
 };
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_BUILTINS_H_