Fix ruby gen command
Fix ruby gen command

protoc-gen-grpc-ruby doesn't work in my machine and google points to this readme as the only occurance...
grpc-ecosystem/grpc-gateway,gengo/grpc-gateway,gengo/grpc-gateway,improbable-io/grpc-gateway,tmc/grpc-gateway,Lantame/grpc-gateway,tmc/grpc-gateway,improbable-io/grpc-gateway,Lantame/grpc-gateway,ilius/grpc-gateway,ilius/grpc-gateway,ilius/grpc-gateway