Don't show console error in a full JupyterLab

### Problem

Starting a full JupyterLab 3.6-based application with `jupyterlite-pyodide-kernel` shows the (harmless) console error:

```
Shared module @jupyterlite/server doesn't exist in shared scope default
```

Harmless, but annoying.

### Proposed Solution

???

### Additional context

things tried
- make all the stuff `optional`
- this happens at import time, before disabled is checked, so can't be solved with token dependencies,
- maybe we just ship the labextension disabled by default.
- `jupyter labextension disable @jupyterlite/pyodide-kernel-extension`
- still gets loaded by webpack machinery (maybe this is fixed in 4?)
- ???