message: [storage] shrink default prune_window
  looks like it's common that people run fullnodes on volumes that are smaller than a few hundred gigabytes.
  Closes:
  Closes:
diff: @@ -31,9 +31,8 @@ impl Default for StorageConfig {
  backup_service_address: SocketAddr::new(IpAddr::V4(Ipv4Addr::LOCALHOST), 6186),
  dir: PathBuf::from("db"),
  grpc_max_receive_len: Some(100_000_000),
  - // At 100 tps on avg, we keep 4~5 days of history.
  - // n.b. Validators have more aggressive override in the config builder.
  - prune_window: Some(40_000_000),
  + // ~50GB state tree history (about 1 day at 100 tps)
  + prune_window: Some(10_000_000),
  data_dir: PathBuf::from("/opt/libra/data"),
  // Default read/write/connection timeout, in milliseconds
  timeout_ms: 30_000,
  