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.

src/common/dcgraph.cpp

@@ -490,11 +490,6 @@ wxSize wxGCDCImpl::GetPPI() const
     return wxDisplay::GetStdPPI();
 }
 
-double wxGCDCImpl::GetDPIScaleFactor() const
-{
-    return m_graphicContext ? m_graphicContext->GetDPIScaleFactor() : 1.0;
-}
-
 int wxGCDCImpl::GetDepth() const
 {
     return 32;