Update grpcio-tools requirement

Updates the requirements on [grpcio-tools](https://github.com/grpc/grpc) to permit the latest version.
- [Release notes](https://github.com/grpc/grpc/releases)
- [Changelog](https://github.com/grpc/grpc/blob/master/doc/grpc_release_schedule.md)
- [Commits](grpc/grpc@v1.56.2...v1.68.1)

---
updated-dependencies:
- dependency-name: grpcio-tools
  dependency-type: direct:development
...

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

setup.py

@@ -167,7 +167,7 @@ def run(self):
         'tensorboardX>=2.6',
         'tqdm',
     ],
-    setup_requires=['grpcio-tools>=1.56.2,<1.66.0'],
+    setup_requires=['grpcio-tools>=1.56.2,<1.69.0'],
     python_requires='>=3.8, <3.12',
     project_urls={
         'Bug Tracker': 'https://github.com/securefederatedai/openfl/issues',