Docker setup is broken

## Context

Reported by olivier@eclipse.builders

## Problem

The [Docker setup](https://docs.celestia.org/how-to-guides/local-devnet#docker-setup) seems broken

```
Starting celestia-appd with command:
/bin/celestia-appd sh -c
celestia-appd init mynode --chain-id private &&
celestia-appd start

Error: unknown command "sh" for "celestia-appd"

Did you mean this?
tx

Run 'celestia-appd --help' for usage.
```

Open the linked local-devnet Docker setup documentation and reproduce the shown startup command to confirm the failure. Trace the documented command invocation and update the setup so the container starts successfully, then rerun the Docker setup to verify the error no longer occurs.

Written by the indexing model from the issue text.