update dangling-alloc-id-ice test

Author: vn-ki

src/test/ui/consts/dangling-alloc-id-ice.rs

@@ -6,7 +6,7 @@ union Foo<'a> {
     long_live_the_unit: &'static (),
 }
 
-const FOO: &() = { //~ ERROR it is undefined behavior to use this value
+const FOO: &() = {
 //~^ ERROR encountered dangling pointer in final constant
     let y = ();
     unsafe { Foo { y: &y }.long_live_the_unit }

src/test/ui/consts/dangling-alloc-id-ice.stderr

@@ -8,18 +8,5 @@ LL | |     unsafe { Foo { y: &y }.long_live_the_unit }
 LL | | };
    | |__^
 
-error[E0080]: it is undefined behavior to use this value
-  --> $DIR/dangling-alloc-id-ice.rs:9:1
-   |
-LL | / const FOO: &() = {
-LL | |
-LL | |     let y = ();
-LL | |     unsafe { Foo { y: &y }.long_live_the_unit }
-LL | | };
-   | |__^ type validation failed: encountered a dangling reference (use-after-free)
-   |
-   = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
-
-error: aborting due to 2 previous errors
+error: aborting due to previous error
 
-For more information about this error, try `rustc --explain E0080`.