Put column images on the right side in generic wxDataViewCtrl

For consistency with wxListCtrl under MSW (which is the only platform
where this change has any effect, as wxHD_BITMAP_ON_RIGHT is only
supported there), put the column images on the right side in
wxDataViewCtrl too.

Closes #13350.

src/generic/datavgen.cpp

@@ -264,7 +264,9 @@ class wxDataViewHeaderWindow : public wxHeaderCtrl
 {
 public:
     wxDataViewHeaderWindow(wxDataViewCtrl *parent)
-        : wxHeaderCtrl(parent)
+        : wxHeaderCtrl(parent, wxID_ANY,
+                       wxDefaultPosition, wxDefaultSize,
+                       wxHD_DEFAULT_STYLE | wxHD_BITMAP_ON_RIGHT)
     {
     }