E0259 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0259.rs

E0259 needs a span_label, updating it from:

error[E0259]: an extern crate named `collections` has already been imported in this module
  --> src/test/compile-fail/E0259.rs:12:1
   |
11 | extern crate collections;
   | ------------------------- previous import of `collections` here
12 | extern crate libc as collections; //~ ERROR E0259
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

To:

error[E0259]: an extern crate named `collections` has already been imported in this module
  --> src/test/compile-fail/E0259.rs:12:1
   |
11 | extern crate collections;
   | ------------------------- previous import of `collections` here
12 | extern crate libc as collections; //~ ERROR E0259
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ already imported