Fix typo: experiements > experiments.
Fix typo: experiements > experiments.

Summary:
Issue fixed: #773

- [ ] All tests pass. Demo project builds and runs.
- [ ] I added tests, an experiment, or detailed why my change isn't tested.
- [ ] I added an entry to the `CHANGELOG.md` for any breaking changes, enhancements, or bug fixes.
- [ ] I have reviewed the [contributing guide](https://github.com/Instagram/IGListKit/blob/master/.github/CONTRIBUTING.md)
Closes https://github.com/Instagram/IGListKit/pull/776

Differential Revision: D5129343

Pulled By: rnystrom

fbshipit-source-id: 127126545f246e5431636642f203c8150b6a547b

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