Update explanation about test annotations

This page [suggests using `compile-pass` as a test annotation](https://github.com/rust-lang/rustc-guide/blob/76be9f99d706d7ac4d10104f44483dd78d6d947a/src/tests/adding.md#tests-that-do-not-result-in-compile-errors). But it will be deprecated in https://github.com/rust-lang/rust/issues/62277. We should update this doc too.