Interface schema links point to wrong content

[dimaqq]

Link checker does its job, but if the library author directs the link to something else, we just get that.

certificate transfer "JSON Schema" points to a schema.py on GitHub.

[james-garner-canonical]

This one needs to be a link (and has the wrong text) https://github.com/canonical/charmlibs/tree/main/interfaces/cos_agent/interface/v0