Bump checkstyle from 8.20 to 8.21
Bump checkstyle from 8.20 to 8.21

Bumps [checkstyle](https://github.com/checkstyle/checkstyle) from 8.20 to 8.21.
- [Release notes](https://github.com/checkstyle/checkstyle/releases)
- [Commits](https://github.com/checkstyle/checkstyle/compare/checkstyle-8.20...checkstyle-8.21)
hazendaz/base-parent