GRPC endpoint clean up. Add missing protocol in doc (#5428)

* GRPC endpoint clean up. Add missing protocol in doc

* Remove GRPC prefix in grpc_server.h/.cc

Author: GuanLuo

docs/protocol/README.md

@@ -43,6 +43,7 @@ plus several extensions that are defined in the following documents:
 - [Shared-memory extension](./extension_shared_memory.md)
 - [Statistics extension](./extension_statistics.md)
 - [Trace extension](./extension_trace.md)
+- [Logging extension](./extension_logging.md)
 
 For the GRPC protocol, the [protobuf
 specification](https://github.com/triton-inference-server/common/blob/main/protobuf/grpc_service.proto)