Fix namespace build when cssparser is disabled

The QT_BEGIN_NAMESPACE was inside "#if TEXTHTMLPARSER" code block,
whereas the QT_END_NAMESPACE was inside a nested "#if CSSPARSER"
block.

Therefore if cssparser was disabled, the file will effectively
have just QT_BEGIN_NAMESPACE, and the build will fail (if it's an
actual namespace build).

Pick-to: 6.9 6.8
Change-Id: Ibd750a71c154cb9596a7227327b7d5b3ab307001
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

src/gui/text/qtexthtmlparser.cpp

@@ -2275,7 +2275,8 @@ bool QTextHtmlParser::nodeIsChildOf(int i, QTextHTMLElements id) const
     return false;
 }
 
-QT_END_NAMESPACE
 #endif // QT_NO_CSSPARSER
 
+QT_END_NAMESPACE
+
 #endif // QT_NO_TEXTHTMLPARSER