user/faq: cleanup

1. warning code block
```{admonition} My markdown link
Here is [markdown link syntax](https://jupyter.org)
```

```{warning} Notes require **no** arguments, so content can start here.
```

2. :ref: → {ref}

https://myst-parser.readthedocs.io/en/v0.13.6/using/syntax.html

Change-Id: If0b0b4bf601a7cb26ccb0f104ce3663271b448ae