O(n log d), deprecate `ordNub`, use `nubOrd`

**What is wrong with the docs?** The haddocs for `ordNub` say it is O(n log n) but the equivalent `nubOrd` function from containers says that it is O(n log d)[^1]. Which is it? Can we deprecate or remove `ordNub` and use `nubOrd` from containers ourselves? Most of our packages depend on containers. [^1]: The "d" here is duplicates, isn't it?