Fix missing docs for QByteArrayList

The public is needed for qdoc which sees class, not struct.

Task-number: QTBUG-42689
Change-Id: I28298b5fd13c6841838634a440bb2f726ddbe7be
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

src/corelib/tools/qbytearraylist.h

@@ -63,6 +63,7 @@ class QByteArrayList : public QList<QByteArray>
 template <> struct QListSpecialMethods<QByteArray>
 #endif
 {
+public:
     inline QByteArray join() const
     { return QtPrivate::QByteArrayList_join(self(), 0, 0); }
     inline QByteArray join(const QByteArray &sep) const