relay: make multicast a desired relay

so we can delete everything except multicast and have
multicast accounts

Signed-off-by: William Casarin <jb55@jb55.com>

crates/notedeck/src/account/relay.rs

@@ -137,6 +137,7 @@ impl RelayDefaults {
             .map(|u| RelaySpec::new(AccountRelayData::canonicalize_url(&u), false, false))
             .collect();
         let bootstrap_relays = [
+            "multicast",
             "wss://relay.damus.io",
             // "wss://pyramid.fiatjaf.com",  // Uncomment if needed
             "wss://nos.lol",