Bump hardhat from 2.20.1 to 2.21.0

Bumps [hardhat](https://github.com/nomiclabs/hardhat) from 2.20.1 to 2.21.0.
- [Release notes](https://github.com/nomiclabs/hardhat/releases)
- [Commits](https://github.com/nomiclabs/hardhat/compare/[email protected]@2.21.0)

---
updated-dependencies:
- dependency-name: hardhat
  dependency-type: direct:development
  update-type: version-update:semver-minor
...

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