Update protobuf requirement

Updates the requirements on [protobuf](https://github.com/protocolbuffers/protobuf) to permit the latest version.

Updates `protobuf` to 6.31.1
- [Release notes](https://github.com/protocolbuffers/protobuf/releases)
- [Changelog](https://github.com/protocolbuffers/protobuf/blob/main/protobuf_release.bzl)
- [Commits](https://github.com/protocolbuffers/protobuf/compare/v3.8.0...v6.31.1)

---
updated-dependencies:
- dependency-name: protobuf
  dependency-version: 6.31.1
  dependency-type: direct:production
  dependency-group: pip
...

Signed-off-by: dependabot[bot] <support@github.com>
diff --git a/python/setup.py b/python/setup.py
index bc3d5c9..11f677a 100644
--- a/python/setup.py
+++ b/python/setup.py
@@ -39,7 +39,7 @@
     license='Apache License, Version 2.0',
     python_requires='>=3.5,<4',
     install_requires=[
-        'protobuf>=3.8.0,<4',
+        'protobuf>=3.8.0,<7',
     ],
     extras_require={
         'tensorflow': ['tensorflow>=1.15,<3'],