Ignore ignore_without_reason pedantic clippy lint in test

    warning: `#[ignore]` without reason
     --> tests/features.rs:2:1
      |
    2 | #[ignore]
      | ^^^^^^^^^
      |
      = help: add a reason with `= ".."`
      = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ignore_without_reason
      = note: `-W clippy::ignore-without-reason` implied by `-W clippy::pedantic`
      = help: to override `-W clippy::pedantic` add `#[allow(clippy::ignore_without_reason)]`

Author: dtolnay

tests/features.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::ignore_without_reason)]
+
 #[test]
 #[ignore]
 fn make_sure_no_proc_macro() {