Use the new doc style for {revision,release}_add.

Summary:
Also fix the 'committer_date' on the PG Storage's revision_add,
that slipped through D676.

Reviewers: Reviewers, douardda

Reviewed By: Reviewers, douardda

Subscribers: douardda, ardumont, swh-public-ci

Differential Revision: https://forge.softwareheritage.org/D698