refactor: apply formatter style to index_fold example

Author: khalidbelk

src/gleam/list.gleam

@@ -785,7 +785,9 @@ pub fn fold_right(
 ///
 /// ```gleam
 /// ["a", "b", "c"]
-/// |> index_fold("", fn(acc, item, index) { acc <> int.to_string(index) <> ":" <> item <> " " })
+/// |> index_fold("", fn(acc, item, index) {
+///      acc <> int.to_string(index) <> ":" <> item <> " "
+/// })
 /// // -> 0:a 1:b 2:c
 /// ```
 ///