Fix generation of static cmis to match protocol
protocol.ml states:
```ocaml
type static_cmi = {
sc_name : string; (* capitalised, e.g. 'Stdlib' *)
sc_content : string;
}
```
but the `gen_static` script was generating:
```ocaml
{sc_name="Stdlib__Buffer.cmi"; sc_content=[%blob ...
```
Fix is to strip the extension.