plenary.enum uses nonexistent metamethod __gt

[jvvv]

Please pardon my bluntness. My lua foo isn't that strong and what I have is fairly rusty. I had to look in my pil books and the reference manuals to refresh my memory about metamethods.

lua/plenary/enum.lua, line 67: lua supports three relational metamethods, __eq, __lt, and __le. As I understand it, the Variant:__gt function will not be recognized by lua.