TD: remove unused class member

Fix compiler warning: -Wunused-private-field

src/Mod/TechDraw/Gui/QGVPage.cpp

@@ -166,7 +166,7 @@ public:
 
 QGVPage::QGVPage(ViewProviderPage* vpPage, QGSPage* scenePage, QWidget* parent)
     : QGraphicsView(parent), m_renderer(Native), drawBkg(true), m_vpPage(nullptr),
-      m_scene(scenePage), balloonPlacing(false), panningActive(false), m_showGrid(false),
+      m_scene(scenePage), balloonPlacing(false), m_showGrid(false),
       m_navStyle(nullptr), d(new Private(this))
 {
     assert(vpPage);

src/Mod/TechDraw/Gui/QGVPage.h

@@ -182,7 +182,6 @@ private:
     TechDraw::DrawView* m_balloonParent;//temp field. used during balloon placing.
 
     QPoint panOrigin;
-    bool panningActive;
 
     bool m_showGrid;
     QPainterPath m_gridPath;