QTextDocument: compile with QT_NO_PRINTER

The implementation of QTextDocument::print() is not available when
QT_NO_PRINTER is defined but the declaration was so when someone is
using this function (and QT_NO_PRINTER) a linker error will occur.

Fixes: QTBUG-56916
Change-Id: I49aaaa643c4d8587a66fc95733060cea11994872
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>

src/gui/text/qtextdocument.h

@@ -221,7 +221,9 @@ public:
 
     bool isModified() const;
 
+#ifndef QT_NO_PRINTER
     void print(QPagedPaintDevice *printer) const;
+#endif
 
     enum ResourceType {
         UnknownResource = 0,