Sync qxmlstream.g with qxmlstreamparser_p.h [2/2]: QT_NAMESPACE macros

Amends 6eb1cdd1c6.

Pick-to: 6.3 6.2
Change-Id: I73f744a537de1ce813e52a6e9934391985d5d5cc
Reviewed-by: Sona Kurazyan <sona.kurazyan@qt.io>

src/corelib/serialization/qxmlstream.g

@@ -219,6 +219,8 @@
 #ifndef QXMLSTREAMPARSER_P_H
 #define QXMLSTREAMPARSER_P_H
 
+QT_BEGIN_NAMESPACE
+
 #ifndef QT_NO_XMLSTREAMREADER
 
 bool QXmlStreamReaderPrivate::parse()
@@ -1551,6 +1553,8 @@ nmtoken ::= COLON;
 
 #endif
 
+QT_END_NAMESPACE
+
 #endif
 
 ./