E0388 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0017.rs

Error E0388 needs a span_label, updating it from:

error[E0388]: cannot borrow data mutably in a static location
  --> src/test/compile-fail/E0017.rs:16:39
   |
16 | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
   |                                       ^^^^^^

To:

error[E0388]: cannot borrow data mutably in a static location
  --> src/test/compile-fail/E0017.rs:16:39
   |
16 | static STATIC_REF: &'static mut i32 = &mut X; //~ ERROR E0017
   |                                       ^^^^^^ cannot mutably borrow in static

[medzin]

I will do it.