update ref file

Author: nikomatsakis

src/test/ui/compare-method/region.stderr

@@ -6,14 +6,6 @@ error[E0276]: impl has stricter requirements than trait
 ...
 22 |     fn foo() where 'a: 'b { }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^ impl has extra requirement `'a: 'b`
-   |
-   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
-   = note: for more information, see issue #18937 <https://github.com/rust-lang/rust/issues/18937>
-note: lint level defined here
-  --> $DIR/region.rs:12:9
-   |
-12 | #![deny(extra_requirement_in_impl)]
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to previous error