chore: update docs

Co-authored-by: Philipp Gackstatter <[email protected]>

src/merkle/smt/mod.rs

@@ -621,7 +621,7 @@ pub(crate) trait SparseMerkleTree<const DEPTH: u8> {
 
     /// Constructs an `InnerNode` representing the sibling pair of which `first_leaf` is a part:
     /// - If `first_leaf` is a right child, the left child is copied from the `parent_node`.
-    /// - If `first_leaf` is a left child, the right child is taken from `iter` if it also mutated
+    /// - If `first_leaf` is a left child, the right child is taken from `iter` if it was also mutated
     ///   or copied from the `parent_node`.
     ///
     /// Returns the `InnerNode` containing the hashes of the sibling pair.