Bump hyper-util from 0.1.20 to 0.1.21

Bumps [hyper-util](https://github.com/hyperium/hyper-util) from 0.1.20 to 0.1.21.
- [Release notes](https://github.com/hyperium/hyper-util/releases)
- [Changelog](https://github.com/hyperium/hyper-util/blob/master/CHANGELOG.md)
- [Commits](hyperium/hyper-util@v0.1.20...v0.1.21)

---
updated-dependencies:
- dependency-name: hyper-util
  dependency-version: 0.1.21
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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Author: dependabot[bot]