Grouped dependency updates being assigned to incorrect group

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Package ecosystem

Cargo

### Package manager version

1.74

### Language version

1.74

### Manifest location and content before the Dependabot update

https://github.com/heroku/languages-github-actions/blob/e280b86033bbe1f1f5a51a87d2dc71e89da09b76/Cargo.toml
https://github.com/heroku/languages-github-actions/blob/e280b86033bbe1f1f5a51a87d2dc71e89da09b76/Cargo.lock

### dependabot.yml content

https://github.com/heroku/languages-github-actions/blob/e280b86033bbe1f1f5a51a87d2dc71e89da09b76/.github/dependabot.yml

### Updated dependency

_No response_

### What you expected to see, versus what you actually saw

Our Dependabot config has the `libcnb*` and `libherokubuildpack` packages assigned to a group named `libcnb` and all other minor/patch dependencies assigned to a group named `rust-dependencies`. The `libcnb` group is defined first, so should "win" if a package could fall into either group.

In this PR, the `libcnb*` packages are incorrectly grouped into the `rust-dependencies` group, rather than their own `libcnb` group:
https://github.com/heroku/languages-github-actions/pull/177

Manually triggering a new Dependabot run (via "Insights" -> Dependency graph -> ... etc) didn't fix the PR.

And in fact the PR was then later recreated again with the same issue:
https://github.com/heroku/languages-github-actions/pull/179

This seems to be a recent regression.

It has also affected other repos, for example this PR too:
https://github.com/heroku/buildpacks-go/pull/193

### Native package manager behavior

_No response_

### Images of the diff or a link to the PR, issue, or logs

The initial broken PR was created in this job:
https://github.com/heroku/languages-github-actions/network/updates/757142572

This is a later rebase job, which I was hoping might fix the PR, but didn't:
https://github.com/heroku/languages-github-actions/network/updates/759606224

And then the second broken PR was opened in:
https://github.com/heroku/languages-github-actions/network/updates/759606988

### Smallest manifest that reproduces the issue

_No response_

Start with the linked .github/dependabot.yml, Cargo.toml, and Cargo.lock, then compare the grouping in PRs 177 and 179 with the expected libcnb and rust-dependencies assignments. Review the linked update and rebase jobs to reproduce the regression; done means libcnb* and libherokubuildpack consistently use libcnb while other minor and patch dependencies use rust-dependencies.

Written by the indexing model from the issue text.