Support use-bound on return position impl trait

[A4-Tacks]

    pub rule foo() -> impl for<'a> PartialEq<&'a str> + Debug + use<'input>
        = $("foo")
    pub rule bar() -> impl for<'a> PartialEq<&'a str> + Debug + use<>
        = { "bar" }

[A4-Tacks]

This is a feature of the new version of Rust, I'm not sure how to make the old version ignore this test