Removes module github.com/grpc-ecosystem/go-grpc-middleware

Closes #675 (closed)

Changelog

grpc module in 1.21 release has introduced a same functionality as go-grpc-middleware provided.

https://github.com/grpc/grpc-go/pull/2696

We don't need to use go-grpc-middleware for chaining anymore.

Release Notes

https://github.com/grpc-ecosystem/go-grpc-middleware/releases/tag/v2.0.0