Don't increase the button height in wxMSWButton::GetFittingSize()

This results in buttons being forced to be too tall when using high DPI
and is useless anyhow, as all callers of this function deal with the
height by increasing it to the minimum acceptable value already (or
discard it entirely in wxMessageDialog::AdjustButtonLabels()).

See #18528.

src/msw/anybutton.cpp

@@ -399,7 +399,6 @@ wxSize wxMSWButton::GetFittingSize(wxWindow *win,
     else
     {
         sizeBtn.x += 3*win->GetCharWidth();
-        sizeBtn.y += win->GetCharHeight()/2;
     }
 
     // account for the shield UAC icon if we have it