Bumps [libsecp256k1](https://github.com/paritytech/libsecp256k1) from 0.6.0 to 0.7.0.
- [Release notes](https://github.com/paritytech/libsecp256k1/releases)
- [Changelog](https://github.com/paritytech/libsecp256k1/blob/master/CHANGELOG.md)
- [Commits](https://github.com/paritytech/libsecp256k1/commits

)

---
updated-dependencies:
- dependency-name: libsecp256k1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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