Revise language around dependent claims

[msporny]

Some people are getting confused by the language in Section 9.6 around atomic claims:

https://w3c.github.io/vc-data-model/#bundling-dependent-claims

The confusion seems to be around us suggesting that atomic claims are a best practice, which they are no longer since we have standardized selective disclosure and unlinkable disclosure schemes.

[msporny]

A PR should be raised that notes that selective/unlinkable disclosure schemes should be used and dependent claims should not be allowed to be disclosed independently of one another.