Ref T13552. When a previously discovered commit becomes reachable from a permanent ref, we re-queue workers to update it. However, the commit may already be marked as "published", so the publish worker may do nothing.
It would perhaps be simpler to not mark the commit as published when it isn't reachable from a permanent ref, but this is tricky because the flag is also part of the "imported / all steps" state (see T13580).
Until that can be cleaned up, just clear the flag.