Bless mir-dump test.

Author: cjgillot

src/test/mir-opt/const_prop/const_prop_fails_gracefully.rs

@@ -25,7 +25,7 @@ fn main() {
 //      ...
 //      _4 = const Scalar(AllocId(1).0x0) : &i32;
 //      _3 = const Scalar(AllocId(1).0x0) : &i32;
-//      _2 = const Scalar(AllocId(1).0x0) : *const i32;
+//      _2 = const Value(Scalar(AllocId(1).0x0)) : *const i32;
 //      ...
 //      _1 = move _2 as usize (Misc);
 //      ...