Bump prost from 0.10.3 to 0.10.4 in /fog/ledger/enclave/trusted

Bumps [prost](https://github.com/tokio-rs/prost) from 0.10.3 to 0.10.4.
- [Release notes](https://github.com/tokio-rs/prost/releases)
- [Commits](tokio-rs/prost@v0.10.3...v0.10.4)

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

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