Add default values for wxRichMessageDialog ctor arguments.

Both "caption" and "style" arguments were documented as having default values,
but didn't really have them. Fix this by actually adding them.

Closes #16524.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@77540 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/richmsgdlg.h

@@ -15,8 +15,8 @@ class WXDLLIMPEXP_CORE wxRichMessageDialog : public wxGenericRichMessageDialog
 public:
     wxRichMessageDialog(wxWindow *parent,
                         const wxString& message,
-                        const wxString& caption,
-                        long style)
+                        const wxString& caption = wxMessageBoxCaptionStr,
+                        long style = wxOK | wxCENTRE)
         : wxGenericRichMessageDialog(parent, message, caption, style)
         { }