bless a miri test

src/tools/miri/tests/fail/erroneous_const2.stderr

@@ -4,9 +4,9 @@ error: any use of this value will cause an error
 LL | const FOO: u32 = [X - Y, Y - X][(X < Y) as usize];
    | --------------    ^^^^^ attempt to compute `5_u32 - 6_u32`, which would overflow
    |
-   = note: `#[deny(const_err)]` on by default
    = 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 #71800 <https://github.com/rust-lang/rust/issues/71800>
+   = note: `#[deny(const_err)]` on by default
 
 error[E0080]: evaluation of constant value failed
   --> $DIR/erroneous_const2.rs:LL:CC