Unsubscribe from topics without leaving them

[rodrigo-o]

This was a TODO comment on attestations that impacts also sync_committees, right now to unsubscribe from a topi we need to leave an rejoin:

  @spec stop_collecting(non_neg_integer()) ::
          {:ok, list(Types.Attestation.t())} | {:error, String.t()}
  def stop_collecting(subnet_id) do
    topic = topic(subnet_id)
    Libp2pPort.leave_topic(topic)
    Libp2pPort.join_topic(topic)
    SyncSubnetInfo.stop_collecting(subnet_id)
  end