Bump keyvalues-serde from 0.2.0 to 0.2.1

Bumps [keyvalues-serde](https://github.com/CosmicHorrorDev/vdf-rs) from 0.2.0 to 0.2.1.
- [Release notes](https://github.com/CosmicHorrorDev/vdf-rs/releases)
- [Commits](CosmicHorrorDev/vdf-rs@serde-v0.2.0...serde-v0.2.1)

---
updated-dependencies:
- dependency-name: keyvalues-serde
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>