It's a missing left-over from the "make the origin-visit immutable" migration.
Kudos to the previous diff [1] which made me raise an eyebrow and then realized
the equivalent method in the cassandra backend was dead code (and it is here as well)
Depends on D3594
[1] https://forge.softwareheritage.org/D3594?vs=12649&id=12665#toc