fix a Stacked Borrows test whose output changed

tests/compile-fail/stacked_borrows/static_memory_modification.rs

@@ -3,6 +3,6 @@ static X: usize = 5;
 #[allow(mutable_transmutes)]
 fn main() {
     let _x = unsafe {
-        std::mem::transmute::<&usize, &mut usize>(&X) //~ ERROR borrow stack
+        std::mem::transmute::<&usize, &mut usize>(&X) //~ ERROR writing to alloc0 which is read-only
     };
 }