cargo: bump thiserror from 1.0.67 to 1.0.68

Bumps [thiserror](https://github.com/dtolnay/thiserror) from 1.0.67 to 1.0.68.
- [Release notes](https://github.com/dtolnay/thiserror/releases)
- [Commits](dtolnay/thiserror@1.0.67...1.0.68)

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

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