message: 1646: Update is_valid doc string
diff: @@ -689,6 +689,7 @@ impl Deploy {
  /// Returns true if and only if:
  /// * the deploy hash is correct (should be the hash of the header), and
  /// * the body hash is correct (should be the hash of the body), and
  + /// * approvals are non empty, and
  /// * all approvals are valid signatures of the deploy hash
  pub fn is_valid(&mut self) -> Result<(), DeployValidationFailure> {
  match self.is_valid.as_ref() {
  