Update mypy-protobuf requirement from <4,>=3.0.0 to >=3.0.0,<5

Updates the requirements on [mypy-protobuf](https://github.com/nipunn1313/mypy-protobuf) to permit the latest version.
- [Changelog](https://github.com/nipunn1313/mypy-protobuf/blob/main/CHANGELOG.md)
- [Commits](nipunn1313/mypy-protobuf@v3.0.0...v4.0.0)

---
updated-dependencies:
- dependency-name: mypy-protobuf
  dependency-version: 4.0.0
  dependency-type: direct:development
...

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

Author: dependabot[bot]

pyproject.toml

@@ -56,7 +56,7 @@ compile_proto = "frequenz.repo.config.setuptools.grpc_tools:CompileProto"
 actor = []
 api = [
   "grpcio-tools >= 1.47.0, < 2",
-  "mypy-protobuf >= 3.0.0, < 4",
+  "mypy-protobuf >= 3.0.0, < 6",
   "setuptools >= 67.6.0, < 81",
 ]
 app = []