Function retire_canonical_alias 

async fn retire_canonical_alias(
    services: &Services,
    room_id: &RoomId,
    deleted: &RoomAliasId,
    sender_user: &UserId,
) -> Result

Removes a deleted alias from the room’s canonical alias state.

The directory entry is authoritative and has already been removed, so this runs on a best-effort basis. A sender lacking permission to send m.room.canonical_alias leaves the stale state event in place.