[presubmit] Enable readability/namespace linter checking.

test/cctest/compiler/c-signature.h

 // Copyright 2014 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_COMPILER_C_SIGNATURE_H_
 #define V8_COMPILER_C_SIGNATURE_H_
 
 #include "src/compiler/machine-type.h"
 
 namespace v8 {
@@ skipping 141 matching lines @@
     this->Set(1, MachineTypeForC<P2>());
     this->Set(2, MachineTypeForC<P3>());
   }
 };
 
 typedef CSignature2<int32_t, int32_t, int32_t> CSignature_i_ii;
 typedef CSignature2<uint32_t, uint32_t, uint32_t> CSignature_u_uu;
 typedef CSignature2<float, float, float> CSignature_f_ff;
 typedef CSignature2<double, double, double> CSignature_d_dd;
 typedef CSignature2<Object*, Object*, Object*> CSignature_o_oo;
-}
-}
-}  // namespace v8::internal::compiler
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_COMPILER_C_SIGNATURE_H_