[presubmit] Enable readability/namespace linter checking.

src/lithium.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_LITHIUM_H_
 #define V8_LITHIUM_H_
 
 #include <set>
 
 #include "src/allocation.h"
@@ skipping 817 matching lines @@
   inline LOperand* Current();
   inline void Advance();
 
  private:
   InputIterator input_iterator_;
   DeepIterator env_iterator_;
 };
 
 class LInstruction;
 class LCodeGen;
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_LITHIUM_H_