[presubmit] Enable readability/namespace linter checking.

src/dateparser.h

 // Copyright 2011 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_DATEPARSER_H_
 #define V8_DATEPARSER_H_
 
 #include "src/allocation.h"
 #include "src/char-predicates.h"
 #include "src/scanner.h"
@@ skipping 348 matching lines @@
   // legacy parser.
   template <typename Char>
   static DateParser::DateToken ParseES6DateTime(
       DateStringTokenizer<Char>* scanner,
       DayComposer* day,
       TimeComposer* time,
       TimeZoneComposer* tz);
 };
 
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_DATEPARSER_H_