upgrade 6.21.0

lib/ArduinoJson/src/ArduinoJson/Deserialization/Readers/IteratorReader.hpp

@@ -1,10 +1,10 @@
 // ArduinoJson - https://arduinojson.org
-// Copyright © 2014-2022, Benoit BLANCHON
+// Copyright © 2014-2023, Benoit BLANCHON
 // MIT License
 
 #pragma once
 
-namespace ARDUINOJSON_NAMESPACE {
+ARDUINOJSON_BEGIN_PRIVATE_NAMESPACE
 
 template <typename TIterator>
 class IteratorReader {
@@ -41,4 +41,5 @@ struct Reader<TSource, typename void_<typename TSource::const_iterator>::type>
       : IteratorReader<typename TSource::const_iterator>(source.begin(),
                                                          source.end()) {}
 };
-}  // namespace ARDUINOJSON_NAMESPACE
+
+ARDUINOJSON_END_PRIVATE_NAMESPACE