chore(deps): update dependency protobuf to v6

Author: renovate[bot]

requirements_dev.txt

@@ -18,7 +18,7 @@ google-cloud-pubsub==2.28.0
 googleapis-common-protos==1.69.1
 grpcio==1.71.0
 grpcio-status==1.71.0
-protobuf==5.29.3
+protobuf==6.30.1
 pytest-aiohttp==1.1.0
 pytest-asyncio==0.25.3
 pytest-mock==3.14.0