Schematic: drop undefined/unused function

eeschema/tools/sch_drawing_tools.h

@@ -57,13 +57,6 @@ public:
     int PlaceImage( const TOOL_EVENT& aEvent );
 
 private:
-    /**
-     * @return the "free" area of the canvas in pixels.
-     * the free area is the area that create no autopan when the mouse cursor
-     * is inside this area
-     */
-    EDA_RECT GetCanvasFreeAreaPixels();
-
     /**
      * Get the next queued text item.
      *