Update protobuf requirement in /src/bindings/python

Updates the requirements on [protobuf](https://github.com/protocolbuffers/protobuf) to permit the latest version.
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/protobuf_release.bzl)
- [Commits](protocolbuffers/protobuf@v3.18.1...v5.26.0)

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

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

src/bindings/python/constraints.txt

@@ -1,7 +1,7 @@
 # used in multiple components
 onnx==1.13.1  # Python bindings, ONNX Frontend
 numpy>=1.16.6,<1.26  # Python bindings, frontends
-protobuf>=3.18.1,<4.0.0  # Python bindings, frontends
+protobuf>=3.18.1,<6.0.0  # Python bindings, frontends
 
 # pytest
 pytest>=5.0,<7.4