Fix regression in sizes of buttons with bitmaps in wxMSW

After changes in 53eff92ea7 (Call AdjustForBitmapMargins() only once in
wxAnyButton, 2021-04-24) only the margin was accounted for, not the
image size.

Closes https://github.com/wxWidgets/wxWidgets/pull/2421

src/msw/anybutton.cpp

@@ -621,7 +621,7 @@ wxSize wxAnyButton::DoGetBestSize() const
     }
 
     if ( m_imageData )
-        AdjustForBitmapMargins(size);
+        AdjustForBitmapSize(size);
 
     return wxMSWButton::IncreaseToStdSizeAndCache(self, size);
 }