Bug: Don't generate wxTreeListCtrl for wxRuby3 (which doesn't support it)

[KeyWorksRW]

Description:

wxTreeListCtrl is supported in wxPython via wx.dataview.TreeListCtrl, which means it needs to get added to our testing suite. However, wxRuby3 doesn't support it. See mcorino/wxRuby3 issue #174. Currently, we try to generate it anyway, causing any generated ruby code that uses it to break.

Code generator for this needs to prevent Ruby code generation for this with the usual warning until/unless support is added to it in wxRuby3.