Bump serde_repr from 0.1.19 to 0.1.20 (#360)

Bumps [serde_repr](https://github.com/dtolnay/serde-repr) from 0.1.19 to 0.1.20.
- [Release notes](https://github.com/dtolnay/serde-repr/releases)
- [Commits](dtolnay/serde-repr@0.1.19...0.1.20)

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

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Author: dependabot[bot]