Bump jekyll from 4.2.0 to 4.2.1

Bumps [jekyll](https://github.com/jekyll/jekyll) from 4.2.0 to 4.2.1.
- [Release notes](https://github.com/jekyll/jekyll/releases)
- [Changelog](https://github.com/jekyll/jekyll/blob/master/History.markdown)
- [Commits](https://github.com/jekyll/jekyll/compare/v4.2.0...v4.2.1)