Fix line numbers in ui test

Author: oli-obk

src/test/ui/cast-to-unsized-trait-object-suggestion.stderr

@@ -7,9 +7,9 @@ error: cast to unsized type: `&{integer}` as `std::marker::Send`
    |           help: try casting to a reference instead: `&Send`
 
 error: cast to unsized type: `std::boxed::Box<{integer}>` as `std::marker::Send`
-  --> $DIR/cast-to-unsized-trait-object-suggestion.rs:16:5
+  --> $DIR/cast-to-unsized-trait-object-suggestion.rs:13:5
    |
-16 |     Box::new(1) as Send;
+13 |     Box::new(1) as Send;
    |     ^^^^^^^^^^^^^^^----
    |                    |
    |                    help: try casting to a `Box` instead: `Box<Send>`