Docs update request: /docs/advanced/proof-of-stake-devnet

Source: https://docs.prylabs.network/docs/advanced/proof-of-stake-devnet

The tutorial does not work anymore. No blocks are being produced. 

Steps to reproduce:

```
git clone https://github.com/rauljordan/eth-pos-devnet && cd eth-pos-devnet
docker-compose pull
docker-compose up -d
```

No blocks are produced


Request: (how can we help?)