FancyToolButton: remove forceVisible

It's never used

Change-Id: Ia2e7ab19685066daf29b5209cb7ea2a7485dfcf2
Reviewed-by: Eike Ziller <eike.ziller@digia.com>

src/plugins/coreplugin/fancyactionbar.h

@@ -57,13 +57,8 @@ public:
     float fader() { return m_fader; }
     void setFader(float value) { m_fader = value; update(); }
 
-    void forceVisible(bool visible);
-
 private slots:
     void actionChanged();
-
-private:
-    bool m_hasForceVisible;
 };
 
 class FancyActionBar : public QWidget