message: fix: fix substitutions field name
diff: @@ -85,6 +85,7 @@ impl PartialOrd for NucSub {
  #[derive(Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Serialize, Deserialize)]
  #[serde(rename_all = "camelCase")]
  pub struct NucSubLabeled {
  + #[serde(rename = "substitution")]
  pub sub: NucSub,
  pub labels: Vec<String>,
  }
  