Add missing wx/scopedptr.h in wxMSW wxFileDialog code

This file uses wxScopedPtr<> and so needs to include this header
explicitly instead of relying on it being included indirectly from some
other header, as happens in the default build, but not always.

Closes #18711.

src/msw/filedlg.cpp

@@ -44,6 +44,7 @@
 
 #include "wx/dynlib.h"
 #include "wx/filename.h"
+#include "wx/scopedptr.h"
 #include "wx/scopeguard.h"
 #include "wx/tokenzr.h"
 #include "wx/modalhook.h"