Documentation of "role" field of Taskprov peer aggregator is inconsistent

[divergentdave]

The initial schema migration has a comment that says the taskprov_peer_aggregators.role column is "the role of this aggregator relative to the peer", while the documentation comment on PeerAggregator::role() says "Retrieve the role of the peer." I think we are going to settle on the source code's interpretation of this field, thus the comment in the schema is wrong. Unfortunately, sqlx's migrations table includes a hash of this migration, so we can't just update the SQL script without some extra manual interventions in deployed environments. We should correct this the next time we make database breaking changes and combine down to one migration script.