E0527 needs to be updated to new format

[sophiajt]

From: src/test/compile-fail/E0527.rs

E0527 needs a span_label, updating it from:

error[E0527]: pattern requires 2 elements but array has 4
  --> src/test/compile-fail/E0527.rs:16:10
   |
16 |         &[a, b] => { //~ ERROR E0527
   |          ^^^^^^

To:

error[E0527]: pattern requires 2 elements but array has 4
  --> src/test/compile-fail/E0527.rs:16:10
   |
16 |         &[a, b] => { //~ ERROR E0527
   |          ^^^^^^ expected 4 elements