[presubmit] Enable readability/namespace linter checking.

test/cctest/types-fuzz.h

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 322 matching lines @@
 
   Region* region() { return region_; }
 
  private:
   Region* region_;
   Isolate* isolate_;
   v8::base::RandomNumberGenerator* rng_;
 };
 
 
-} }  // namespace v8::internal
+}  // namespace internal
+}  // namespace v8
 
 #endif