Remove init() function declaration.

Fix doc error. This function is not used in Qt 5
and there is no definition for it.

Change-Id: Id7e4fe1ada54005f65a559ae1ab393d011c37480
Reviewed-by: Timur Pocheptsov <Timur.Pocheptsov@digia.com>

src/widgets/widgets/qmacnativewidget_mac.h

@@ -52,7 +52,6 @@ public:
     NSView *nativeView() const;
 
 protected:
-    void init(NSView *parentView);
     bool event(QEvent *ev);
 
 private: