update consul command

[gelpenaddict]

https://cortexmetrics.io/docs/getting-started/#horizontally-scale-out

> docker run -d --name=consul --network=cortex -e CONSUL_BIND_INTERFACE=eth0 consul
Unable to find image 'consul:latest' locally
docker: Error response from daemon: manifest for consul:latest not found: manifest unknown: manifest unknown.
See 'docker run --help'.

Consul in Docker was deprecated and they point to hashicorp/consul:
https://hub.docker.com/_/consul

Users of Docker images should pull from hashicorp/consul instead of consul.