radicle/bootstrap: Add rosa.radicle.xyz — heartwood

This is stacked on heartwood/patches/e01a58a041f979621a718f31117ec393ab8f30e3.

I realized that rosa.radicle.xyz is not even listed as bootstrap node.

     /// Bootstrap nodes for this network.
     pub fn bootstrap(&self) -> Vec<(Alias, ProtocolVersion, ConnectAddress)> {
         match self {
             Self::Main => [(
                 "iris.radicle.xyz",
                 seeds::RADICLE_NODE_BOOTSTRAP_IRIS.clone(),
             )]
             Self::Main => [
                 (
                     "iris.radicle.xyz",
                     seeds::RADICLE_NODE_BOOTSTRAP_IRIS.clone(),
                 ),
                 (
                     "rosa.radicle.xyz",
                     seeds::RADICLE_NODE_BOOTSTRAP_ROSA.clone(),
                 ),
             ]
             .into_iter()
             .map(|(a, s)| (Alias::new(a), 1, s))
             .collect(),