Fix DPI value in Cairo printing on MSW.

Linux will need a different fix.

Fixes https://gitlab.com/kicad/code/kicad/-/issues/20477 on MSW


(cherry picked from commit 2a36da6723)

Co-authored-by: Alex Shvartzkop <dudesuchamazing@gmail.com>

common/gal/cairo/cairo_print.cpp

@@ -95,7 +95,8 @@ CAIRO_PRINT_CTX::CAIRO_PRINT_CTX( wxDC* aDC ) :
     m_hdc = g->GetHDC();
     m_surface = cairo_win32_printing_surface_create( static_cast<HDC>( m_hdc ) );
     m_ctx = cairo_create( m_surface );
-    m_dpi = GetDeviceCaps( static_cast<HDC>( m_hdc ), LOGPIXELSX );
+    wxASSERT( aDC->GetPPI().x == aDC->GetPPI().y );
+    m_dpi = aDC->GetPPI().x;
 #endif /* __WXMSW__ */
 
 #ifdef __WXMAC__