Bump submodules/protobuf from 4b159e0 to cf6ea88

Bumps [submodules/protobuf](https://github.com/Jelly-RDF/jelly-protobuf) from `4b159e0` to `cf6ea88`.
- [Release notes](https://github.com/Jelly-RDF/jelly-protobuf/releases)
- [Commits](Jelly-RDF/jelly-protobuf@4b159e0...cf6ea88)

---
updated-dependencies:
- dependency-name: submodules/protobuf
  dependency-version: cf6ea8844f50e2e679e1b08950d39e4311a66b4a
  dependency-type: direct:production
...

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Author: dependabot[bot]