message: trivial: improve error message
  Closes:
diff: @@ -366,8 +366,8 @@ where
  ) -> Result<AccumulatorConsistencyProof> {
  ensure!(
  sub_acc_leaves <= self.num_leaves,
  - "The other accumulator is bigger than this one. self.num_leaves: {}. \
  - sub_acc_leaves: {}.",
  + "Can't get accumulator consistency proof for a version newer than the local version. \
  + Local next version: {}, asked next version: {}",
  self.num_leaves,
  sub_acc_leaves,
  );
  