Updated protoc generated files and doc

Author: cmaglie

docs/CONTRIBUTING.md

@@ -82,7 +82,7 @@ If you're working on the gRPC interface you will also have to:
 - download and install the [protoc][6] compiler (use the version required to match the generated code, please note that
   the latest releases does not follow semantic versioning anymore so, for example, the version 5.26.1 must be searched
   as 26.1 dropping the major number)
-- install `protoc-gen-go` using: `go install google.golang.org/protobuf/cmd/[email protected].1` (use the version
+- install `protoc-gen-go` using: `go install google.golang.org/protobuf/cmd/[email protected].2` (use the version
   required to match the generated code)
 - install `protoc-gen-go-grpc` using: `go install google.golang.org/grpc/cmd/[email protected]` (use the version
   required to match the generated code)