[presubmit] Enable readability/namespace linter checking.

src/base/atomicops_internals_ppc_gcc.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.
 
 // This file is an internal atomic implementation, use atomicops.h instead.
 //
 
 #ifndef V8_BASE_ATOMICOPS_INTERNALS_PPC_H_
 #define V8_BASE_ATOMICOPS_INTERNALS_PPC_H_
 
@@ skipping 144 matching lines @@
   MemoryBarrier();
   return value;
 }
 
 inline Atomic64 Release_Load(volatile const Atomic64* ptr) {
   MemoryBarrier();
   return *ptr;
 }
 
 #endif
-}
-}  // namespace v8::base
+}  // namespace base
+}  // namespace v8
 
 #endif  // V8_BASE_ATOMICOPS_INTERNALS_PPC_GCC_H_