cleanup

src/ruby/ext/grpc/rb_call.c

src/ruby/ext/grpc/rb_channel.c

src/ruby/ext/grpc/rb_completion_queue.c

src/ruby/ext/grpc/rb_completion_queue.h

src/ruby/ext/grpc/rb_grpc.c

src/ruby/ext/grpc/rb_server.c

src/ruby/spec/channel_connection_spec.rb