E0038 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0038.rs

Error E0038 needs a span_label, updating it from:

error[E0038]: the trait `Trait` cannot be made into an object
  --> src/test/compile-fail/E0038.rs:15:1
   |
15 | fn call_foo(x: Box<Trait>) { //~ ERROR E0038
   | ^
   |
   = note: method `foo` references the `Self` type in its arguments or return type

To:

error[E0038]: the trait `Trait` cannot be made into an object
  --> src/test/compile-fail/E0038.rs:15:1
   |
15 | fn call_foo(x: Box<Trait>) { //~ ERROR E0038
   | ^ `Trait` cannot be made into an object
   |
   = note: method `foo` references the `Self` type in its arguments or return type

Bonus: not sure how difficult this would be, but we should underline where the issue occurs if possible. Something like:

error[E0038]: the trait `Trait` cannot be made into an object
  --> src/test/compile-fail/E0038.rs:15:1
   |
15 | fn call_foo(x: Box<Trait>) { //~ ERROR E0038
   |                ^^^^^^^^^^ `Trait` cannot be made into an object
   |
   = note: method `foo` references the `Self` type in its arguments or return type