Remove dead method.

Fix Qt 5 TODO

Change-Id: I9a12cc07ebc7c039bbeb53922b0539f177b226f8
Reviewed-by: Samuel Rødal <samuel.rodal@nokia.com>

src/gui/image/qpixmap.cpp

@@ -1003,14 +1003,6 @@ bool QPixmap::isDetached() const
     return data && data->ref.load() == 1;
 }
 
-/*! \internal
-  ### Qt5 - remove me.
-*/
-void QPixmap::deref()
-{
-    Q_ASSERT_X(false, "QPixmap::deref()", "Do not call this function anymore!");
-}
-
 /*!
     Replaces this pixmap's data with the given \a image using the
     specified \a flags to control the conversion.  The \a flags

src/gui/image/qpixmap.h

@@ -174,7 +174,6 @@ private:
 
     QPixmap(const QSize &s, int type);
     void doInit(int, int, int);
-    void deref();
     Q_DUMMY_COMPARISON_OPERATOR(QPixmap)
     friend class QPlatformPixmap;
     friend class QBitmap;