Ignore mixed_attributes_style clippy lint

    warning: item has both inner and outer attributes
     --> tests/test_lints.rs:5:1
      |
    5 | / #[test]
    6 | | fn test_unused_qualifications() {
    7 | |     #![deny(unused_qualifications)]
      | |___________________________________^
      |
      = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#mixed_attributes_style
      = note: `#[warn(clippy::mixed_attributes_style)]` on by default

tests/test_lints.rs

@@ -1,3 +1,5 @@
+#![allow(clippy::mixed_attributes_style)]
+
 use thiserror::Error;
 
 pub use std::error::Error;