ETH - Better container name in beacon yaml

https://github.com/flare-foundation/fdc-suite-deployment/blob/main/nodes-mainnet/eth/beacon.yaml#L22

The default container name should be "ethereum" and not "geth", aligning it with compose configuration.

Also the port 8551 should be added in https://github.com/flare-foundation/fdc-suite-deployment/blob/main/nodes-mainnet/eth/docker-compose.yaml#L18