Fix drawing of corners in wxGraphicsContext::DrawLines()

Close the path corresponding to the polygon to ensure that the starting
and finishing edges are joined correctly, which wasn't the case before
as could be easily seen when using thicker pens.

Closes #22440.

src/common/graphcmn.cpp

@@ -835,6 +835,7 @@ void wxGraphicsContext::DrawLines( size_t n, const wxPoint2DDouble *points, wxPo
     path.MoveToPoint(points[0].m_x, points[0].m_y);
     for ( size_t i = 1; i < n; ++i)
         path.AddLineToPoint( points[i].m_x, points[i].m_y );
+    path.CloseSubpath();
     DrawPath( path , fillStyle);
 }