Bump shellexpand from 2.1.0 to 2.1.2 in /src/rust/engine (pantsbuild#…

…16474)

Bumps [shellexpand](https://gitlab.com/ijackson/rust-shellexpand) from 2.1.0 to 2.1.2.
- [Release notes](https://gitlab.com/ijackson/rust-shellexpand/tags)
- [Commits](https://gitlab.com/ijackson/rust-shellexpand/commits/shellexpand/2.1.2)

---
updated-dependencies:
- dependency-name: shellexpand
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>