Bump tests/restheart from 9d4ce1c to f551d2b

Bumps [tests/restheart](https://github.com/SoftInstigate/restheart) from `9d4ce1c` to `f551d2b`.
- [Release notes](https://github.com/SoftInstigate/restheart/releases)
- [Commits](SoftInstigate/restheart@9d4ce1c...f551d2b)

---
updated-dependencies:
- dependency-name: tests/restheart
  dependency-type: direct:production
...

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