Listing ontologies with `runoak ontologies` fails with given example

The `runoak ontologies` command doesn't work as described in its docs:
```
$ runoak -i ubergraph ontologies
FileNotFoundError: [Errno 2] No such file or directory: 'ubergraph'

During handling of the above exception, another exception occurred:

ValueError: unknown url type: 'ubergraph'

$ runoak -i ubergraph: ontologies
aism/aism-base.owl
bspo.owl
chebi.owl
cl/cl-base.owl
cob/cob-base.owl
...
```

so mostly it just needs a terminal colon

Locate the documentation example for the `runoak ontologies` command and compare it with the two invocations shown in the issue. Update the example so it matches the working form, then run the documented command and confirm that it lists ontologies successfully.

Written by the indexing model from the issue text.