[presubmit] Enable readability/namespace linter checking.

src/x64/assembler-x64-inl.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_X64_ASSEMBLER_X64_INL_H_
 #define V8_X64_ASSEMBLER_X64_INL_H_
 
 #include "src/x64/assembler-x64.h"
 
 #include "src/base/cpu.h"
@@ skipping 611 matching lines @@
   *p = disp;
   len_ += sizeof(int32_t);
 }
 
 void Operand::set_disp64(int64_t disp) {
   DCHECK_EQ(1, len_);
   int64_t* p = reinterpret_cast<int64_t*>(&buf_[len_]);
   *p = disp;
   len_ += sizeof(disp);
 }
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_X64_ASSEMBLER_X64_INL_H_