unbound-checkconf does not allow module-config with "python respip dns64"

[marcos-ng]

Support for respip and dns64 was added with feeebc95f875ed378848ffc4441e5a66bdf5c50b.

However unbound-checkconf does not show that python is supported with these modules: https://github.com/NLnetLabs/unbound/blob/98f42578905f802bffb3b3ecbb0e39d6784f7544/smallapp/unbound-checkconf.c#L794

Other than allowing it in unbound-checkconf, are there additional changes/fixes needed for the following to work?

module-config: "python respip dns64 validator iterator"

A quick test showed the correct behavior with the above config on 1.24.1.