docs: improve Error When DA Node Connection Fails

https://github.com/deltadevsde/prism/blob/2666b43495f0a28db804868c9108ebadbe9a5bb5/crates/node_types/prover/src/prover/mod.rs#L148

When starting the prover and the connection with the DA node fails the logs show the following:
```
Error: Custom { kind: Other, error: "Failed to start DataAvailabilityLayer" }
```

Instead, I expect more information on why it fails. It seems that the underlying error is not passed to the error printed.
In my scenario, the API returns `{"error":{"code":-32601,"message":"method 'header.Subscribe' not supported in this mode (no out channel support)"},"id":1,"jsonrpc":"2.0"}` because the node was not fully synced.
Forwarding the error is important for the user of prism to be able to debug issues properly.