Cargo: Bump ctor from 0.2.6 to 0.2.8

Bumps [ctor](https://github.com/mmastrac/rust-ctor) from 0.2.6 to 0.2.8.
- [Commits](https://github.com/mmastrac/rust-ctor/commits)

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

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