Bump libcnb* from 0.30.0 to 0.30.2 in the rust-dependencies group (#462)

* 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 0.30.0 to 0.30.2
- [Release notes](https://github.com/heroku/libcnb.rs/releases)
- [Changelog](https://github.com/heroku/libcnb.rs/blob/main/CHANGELOG.md)
- [Commits](heroku/libcnb.rs@v0.30.0...v0.30.2)

---
updated-dependencies:
- dependency-name: libherokubuildpack
  dependency-version: 0.30.2
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: rust-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

* Refresh lockfile

* Bump MSRV

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Ed Morley <501702+edmorley@users.noreply.github.com>

Author: dependabot[bot]

Cargo.lock

@@ -1,7 +1,7 @@
 [package]
 name = "python-buildpack"
 edition = "2024"
-rust-version = "1.89"
+rust-version = "1.91"
 # Disable automatic integration test discovery, since we import them in main.rs (see comment there).
 autotests = false