fix test output

Author: pietroalbini

src/test/ui/consts/static_mut_containing_mut_ref2.rs

@@ -4,6 +4,5 @@ static mut STDERR_BUFFER_SPACE: u8 = 0;
 
 pub static mut STDERR_BUFFER: () = unsafe { *(&mut STDERR_BUFFER_SPACE) = 42; };
 //~^ ERROR references in statics may only refer to immutable values
-//~| ERROR static contains unimplemented expression type
 
 fn main() {}

src/test/ui/consts/static_mut_containing_mut_ref2.stderr

@@ -4,13 +4,6 @@ error[E0017]: references in statics may only refer to immutable values
 LL | pub static mut STDERR_BUFFER: () = unsafe { *(&mut STDERR_BUFFER_SPACE) = 42; };
    |                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^ statics require immutable values
 
-error[E0019]: static contains unimplemented expression type
-  --> $DIR/static_mut_containing_mut_ref2.rs:5:45
-   |
-LL | pub static mut STDERR_BUFFER: () = unsafe { *(&mut STDERR_BUFFER_SPACE) = 42; };
-   |                                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-Some errors occurred: E0017, E0019.
-For more information about an error, try `rustc --explain E0017`.
+For more information about this error, try `rustc --explain E0017`.