Fix PVS-studio error

- QGCMark duplicates field & method from base class

src/Mod/TechDraw/Gui/QGICMark.cpp

@@ -41,7 +41,6 @@ using namespace TechDrawGui;
 
 QGICMark::QGICMark(int index) : QGIVertex(index)
 {
-    projIndex = 0;
     m_size = 3.0;
     m_width = 0.75;
     draw();

src/Mod/TechDraw/Gui/QGICMark.h

@@ -41,8 +41,6 @@ public:
     virtual QRectF boundingRect() const override;
     virtual QPainterPath shape() const override;
 
-    int getProjIndex() const { return projIndex; }
-
     void draw(void);
     float getSize() { return m_size; }
     void setSize(float s);
@@ -53,7 +51,6 @@ public:
     double getMarkFuzz(void) const;
 
 protected:
-    int projIndex;
     QColor getCMarkColor();
 
 private: