message: adapt try build expected error to new output
diff: @@ -7,4 +7,4 @@ error[E0502]: cannot borrow `layer` as immutable because it is also borrowed as
  | mutable borrow occurs here
  | mutable borrow later used here
  9 | let _ = layer.defn();
  - | ^^^^^ immutable borrow occurs here
  + | ^^^^^^^^^^^^ immutable borrow occurs here
  