splitgraph.yml generator: no lists for JSONSchema with `oneOf` with a single option

[mildbyte]

If a schema has a oneOf with only a single option, there's no need to generate a list with multiple potential options to go into this oneOf:

sgr/splitgraph/cloud/project/generation.py

Line 86 in bc7ea99

def _get_oneof_example(obj: Dict[str, Any]) -> CS: