add needs-unwind to UI test

the `tail-expr-lock-poisoning` UI test uses the `panic::catch_unwind`
API so it relies on unwinding being implemented. this test ought not to
run on targets that do not support unwinding. add the `needs-unwind`
attribute to signal this

Author: japaric

tests/ui/lifetimes/tail-expr-lock-poisoning.rs

@@ -3,6 +3,7 @@
 //@ [edition2024] compile-flags: -Zunstable-options
 //@ [edition2024] edition: 2024
 //@ run-pass
+//@ needs-unwind
 #![cfg_attr(edition2024, feature(shorter_tail_lifetimes))]
 
 use std::sync::Mutex;