Bump libherokubuildpack in the rust-dependencies group

Bumps the rust-dependencies group with 1 update: [libherokubuildpack](https://github.com/heroku/libcnb.rs).


Updates `libherokubuildpack` from 0.28.0 to 0.28.1
- [Release notes](https://github.com/heroku/libcnb.rs/releases)
- [Changelog](https://github.com/heroku/libcnb.rs/blob/main/CHANGELOG.md)
- [Commits](heroku/libcnb.rs@v0.28.0...v0.28.1)

---
updated-dependencies:
- dependency-name: libherokubuildpack
  dependency-version: 0.28.1
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: rust-dependencies
...

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Author: dependabot[bot]