Change file name to match documentation

Voronoi_diagram_2/doc/Voronoi_diagram_2/CGAL/draw_voronoi_diagram_2.h

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+namespace CGAL {
+  
+/*!
+\ingroup PkgDrawVoronoiDiagram2
+
+Open a new window and draw `av2`, the `Voronoi_diagram_2` constructed from a Delaunay Graph which is a model of `DelaunayGraph_2` concept.
+The class `Voronoi_diagram_2` provides an adaptor to view a triangulated Delaunay graph as their dual subdivision, the 
+Voronoi diagram. The function is blocking, that is the program continues as soon as the user closes the window. 
+ This function requires CGAL_Qt5, and is only available if the flag CGAL_USE_BASIC_VIEWER is defined at compile time.
+\tparam V2 a model of the `Voronoi2` concept.
+\param av2 the voronoi diagram to draw.
+
+*/
+template<class V2>
+void draw(const V2& av2);
+
+} /* namespace CGAL */