[presubmit] Enable readability/namespace linter checking.

test/cctest/test-dictionary.cc

 // Copyright 2011 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 221 matching lines @@
 
 TEST(ObjectHashTableCausesGC) {
   i::FLAG_stress_compaction = false;
   LocalContext context;
   v8::HandleScope scope(context->GetIsolate());
   Isolate* isolate = CcTest::i_isolate();
   TestHashMapCausesGC(ObjectHashTable::New(isolate, 1));
 }
 #endif
 
-}
+}  // namespace