Bump thiserror from 1.0.65 to 1.0.68 in /divviup/rust

Bumps [thiserror](https://github.com/dtolnay/thiserror) from 1.0.65 to 1.0.68.
- [Release notes](https://github.com/dtolnay/thiserror/releases)
- [Commits](dtolnay/thiserror@1.0.65...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>

divviup/rust/Cargo.toml

@@ -13,4 +13,4 @@ janus_messages = "0.7.2"
 jni = "0.21.1"
 prio = "0.16.7"
 rand = "0.8.5"
-thiserror = "1.0.65"
+thiserror = "1.0.68"