Remove the concept of an account contact from all of boulder except the
WFE. Specifically:
- Delete the UpdateRegistrationContact methods from the RA and SA
- Remove all understanding of the Contact field from the RA and SA's
NewRegistration methods
- Remove the Contact field from corepb.Registration to ensure it can
never be communicated anywhere
Note that this does not remove the Contact field from core.Registration,
as that represents an ACME API type, and we're still willing to parse
the Contact field from incoming new-account requests.
Fixes https://github.com/letsencrypt/boulder/issues/8199
d7e4ed18ad