build(deps): bump hkdf from 0.12.3 to 0.12.4 (#161)

Bumps [hkdf](https://github.com/RustCrypto/KDFs) from 0.12.3 to 0.12.4.
- [Commits](RustCrypto/KDFs@hkdf-v0.12.3...hkdf-v0.12.4)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>