QJsonArray: symmetrize QDataStream op>>/<<

In operator<<(), stream the QJsonDocument directly, instead of
toJson(Compact).

This is how QJsonDocument operator<<() also does things, but that
knowledge should be need-to-know, and QJsonArray doesn't, seeing as
operator>>() just streams a QJsonDocument, and then calls toArray().

Pick-to: 6.7 6.6 6.5
Change-Id: Ia378bf0fb04ce33e3af24a2ce67778e89c41e31a
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

src/corelib/serialization/qjsonarray.cpp

@@ -1076,9 +1076,7 @@ QDebug operator<<(QDebug dbg, const QJsonArray &a)
 #ifndef QT_NO_DATASTREAM
 QDataStream &operator<<(QDataStream &stream, const QJsonArray &array)
 {
-    QJsonDocument doc{array};
-    stream << doc.toJson(QJsonDocument::Compact);
-    return stream;
+    return stream << QJsonDocument{array};
 }
 
 QDataStream &operator>>(QDataStream &stream, QJsonArray &array)