E0389 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0389.rs

E0389 needs a span_label, taking it from:

error[E0389]: cannot assign to data in a `&` reference
  --> src/test/compile-fail/E0389.rs:18:5
   |
18 |     fancy_ref.num = 6; //~ ERROR E0389
   |     ^^^^^^^^^^^^^^^^^

To:

error[E0389]: cannot assign to data in a `&` reference
  --> src/test/compile-fail/E0389.rs:18:5
   |
18 |     fancy_ref.num = 6; //~ ERROR E0389
   |     ^^^^^^^^^^^^^^^^^ assignment into an immutable reference

[ahmedcharles]

src/test/compile-fail/E0389.rs doesn't exist and I can't seem to write a test file that triggers this error.

[sophiajt]

Have you done a 'git pull' recently? Iirc, it's one of the test files that just landed.

[ahmedcharles]

It's there now, so it must have landed recently. Thanks.