Bump protobuf from 3.20.3 to 5.29.6

Bumps [protobuf](https://github.com/protocolbuffers/protobuf) from 3.20.3 to 5.29.6.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Commits](https://github.com/protocolbuffers/protobuf/commits)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-version: 5.29.6
  dependency-type: direct:production
...

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

Author: dependabot[bot]

pyproject.toml

@@ -28,7 +28,7 @@ dependencies = [
     "gtfs-realtime-bindings>=1.0.0,<2",
     "importlib-metadata>=4.0.0,<5",
     "lxml>=4.7.1,<6",
-    "protobuf>=3.20.0,<4",
+    "protobuf>=3.20.0,<6",
     "pydantic>=2.8,<2.9",
     "python-dateutil>=2.8,<2.9",
     "requests>=2.25.0,<3",