Remove GetDPIScaleFactor from wxDC and wxGraphicsContext

This reverts most of the changes from ee2b02614e (Add GetDPIScaleFactor to wxDC
and wxGraphicsContext, 2022-04-16).

This is not supposed to be used to scale pixels, FromDIP will be added instead.

Temporary use scale=1 in the drawing sample until FromDIP is added.

samples/drawing/drawing.cpp

@@ -574,7 +574,7 @@ void MyCanvas::DrawTestPoly(wxDC& dc)
     wxBrush brushHatch(*wxRED, wxBRUSHSTYLE_FDIAGONAL_HATCH);
     dc.SetBrush(brushHatch);
 
-    double scale = dc.GetDPIScaleFactor();
+    double scale = 1.0;
 
     wxPoint star[5];
     star[0] = scale * wxPoint(100, 60);