Consider updating `super` usage

On Python 3, `super` can simply be used as `super().method_name(...)` instead of `super(ClassName, self).method_name(*args, **kwargs)`.

Note that these changes are not worth making unless they can be more or less automated using search-and-replace, potentially using regex. It might also make sense to split up the work across multiple PRs instead of making all of the changes at the same time. These changes will need to be carefully vetted to ensure that we're not modifying behavior when modifying the `super` call.