Update const eval uninhabited messages

Author: varkor

src/test/ui/consts/const-eval/ub-uninhabit.stderr

@@ -2,9 +2,11 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-uninhabit.rs:19:1
    |
 LL | const BAD_BAD_BAD: Bar = unsafe { mem::transmute(()) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^------------------^^^
+   |                                   |
+   |                                   entered unreachable code
    |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   = note: #[deny(const_err)] on by default
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-uninhabit.rs:22:1
@@ -18,9 +20,9 @@ error[E0080]: it is undefined behavior to use this value
   --> $DIR/ub-uninhabit.rs:25:1
    |
 LL | const BAD_BAD_ARRAY: [Bar; 1] = unsafe { mem::transmute(()) };
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered a value of an uninhabited type at [0]
-   |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^------------------^^^
+   |                                          |
+   |                                          entered unreachable code
 
 error: aborting due to 3 previous errors