Ignore nightly's new elided_named_lifetimes lint in generated code

    warning: the type of the `self` parameter does not need to be arbitrary
        --> tests/test.rs:1656:24
         |
    1656 |         async fn f(mut self: &Self) {
         |                        ^^^^^^^^^^^ help: consider to change this parameter to: `&'life0 self`
         |
         = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#needless_arbitrary_self_type
         = note: `#[warn(clippy::needless_arbitrary_self_type)]` on by default

Ignore needless_arbitrary_self_type clippy lint in generated code