remove incorrect lifetime annotation

[aliemjay]

Hi,
rustc was previously accepting this incorrect code:

async fn test<'a>() { // `'a`, being a lifetime parameter, must be longer than the entire function body
    let f = |_: &'a str| {}; // the argument is required to outlive `'a`
    f(&String::new()); // an argument of shorter lifetime is passed!
}

Now that this is fixed, we found that FGC.rs relies on this bug. This PR tries to fix this.

[nielsdos]

LGTM, thanks!