[presubmit] Enable readability/namespace linter checking.

test/cctest/test-unscopables-hidden-prototype.cc

 // 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.
 
 // TODO(mythria): Remove this after this flag is turned on globally
 #define V8_IMMINENT_DEPRECATION_WARNINGS
 
 #include <stdlib.h>
 
 #include "src/v8.h"
@@ skipping 102 matching lines @@
                          "var x = 0;"
                          "hidden_prototype.x = 6;"
                          "object[Symbol.unscopables] = {x: true};"
                          "with (object) {"
                          "  result = x;"
                          "}"
                          "result")
                   ->Int32Value(current_context)
                   .FromJust());
 }
-}
+
+}  // namespace