Update RxIGListKit link on Best Practices & FAQ (#1375)
Update RxIGListKit link on Best Practices & FAQ (#1375)

Summary:
## Changes in this pull request
Updated the link to RxIGListKit as the current one points to a dead end. Simple documentation update, no code changes.

Issue fixed: #

### Checklist

- [x] All tests pass. Demo project builds and runs.
- [x] I added tests, an experiment, or detailed why my change isn't tested.
- [x] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [x] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Pull Request resolved: https://github.com/Instagram/IGListKit/pull/1375

Reviewed By: bdotdub

Differential Revision: D18525301

Pulled By: iperry90

fbshipit-source-id: 650c6828b5a9ba256d2aa6b0c1abb27d3de43a8c

Instagram/IGListKit,Instagram/IGListKit,Instagram/IGListKit,Instagram/IGListKit,Instagram/IGListKit