Bump io-ts from 2.2.20 to 2.2.21

Bumps [io-ts](https://github.com/gcanti/io-ts) from 2.2.20 to 2.2.21.
- [Release notes](https://github.com/gcanti/io-ts/releases)
- [Changelog](https://github.com/gcanti/io-ts/blob/master/CHANGELOG.md)
- [Commits](https://github.com/gcanti/io-ts/commits)

---
updated-dependencies:
- dependency-name: io-ts
  dependency-type: direct:development
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>