This `raft_topology_update_ip` call always returns after `t.find(raft_id)`
returns `nullptr`, so it effectively does nothing. It's not a bug, since
there is no reason to update `system.peers` for left nodes anyway. We
delete the rows corresponding to left nodes in `process_left_node` (called
just above).
Closesscylladb/scylladb#27899