chore: fix type hinting

Author: remyleone

scaleway-core/scaleway_core/utils/resolve_one_of.py

@@ -15,6 +15,8 @@ class OneOfPossibility(Generic[T]):
     default: Optional[T | ProfileDefaults] = None
     marshal_func: Optional[Callable[[T, T | None], Dict[str, Any]]] = None
 
+    marshal_func: Optional[T] = None
+
 
 def resolve_one_of(
     possibilities: List[OneOfPossibility[Any]], is_required: bool = False