[has-PR] align ISO mDL CBOR format identifier to the ISO draft

[Kristina Yasuda]

ISO draft currently uses mso_mdoc , which also better aligns to jwt_vc format: mso and jwt explaining how the credential format is secured/signed, and mdoc and vc parts explaining which data model is used.

Previously agreed in the WG to keep aligning to the ISO draft, when we merged PR #224.

addressed in PR #315.