[presubmit] Enable readability/namespace linter checking.

src/icu_util.h

 // Copyright 2013 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_ICU_UTIL_H_
 #define V8_ICU_UTIL_H_
 
 namespace v8 {
 
 namespace internal {
 
 // Call this function to load ICU's data tables for the current process.  This
 // function should be called before ICU is used.
 bool InitializeICU(const char* icu_data_file);
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_ICU_UTIL_H_