[presubmit] Enable readability/namespace linter checking.

src/regexp/mips64/regexp-macro-assembler-mips64.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_REGEXP_MIPS_REGEXP_MACRO_ASSEMBLER_MIPS_H_
 #define V8_REGEXP_MIPS_REGEXP_MACRO_ASSEMBLER_MIPS_H_
 
 #include "src/macro-assembler.h"
 #include "src/mips64/assembler-mips64.h"
 #include "src/regexp/regexp-macro-assembler.h"
@@ skipping 244 matching lines @@
   Label backtrack_label_;
   Label exit_label_;
   Label check_preempt_label_;
   Label stack_overflow_label_;
   Label internal_failure_label_;
 };
 
 #endif  // V8_INTERPRETED_REGEXP
 
 
-}}  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif  // V8_REGEXP_MIPS_REGEXP_MACRO_ASSEMBLER_MIPS_H_