Revert misguided delete

I was wrong on two accounts with https://github.com/dimagi/commcare-hq/pull/3243. First, I looked for the use of `listsort` throughout the code, when it was actually just called `sort`. Second, I was right that `SortedDict` needs to be imported, however that never caused an issue because this was only ever used for a list, and that code was never called.