Bug: `begin%e try` AST change

[EmileTrotignon]

The following code has an AST change :

let a =
  begin%e try f x i with
  | A -> f aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
  | B -> bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
  end

it gets transformed into:

let a =
  begin%e
    try%e f x i with
    | A -> f aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
    | B -> bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb
  end

[EmileTrotignon]

fixed in #2666