Ignore extra_unused_type_parameters clippy lint in test

    error: type parameter goes unused in function definition
      --> tests/test_from.rs:51:15
       |
    51 | fn assert_impl<T: From<io::Error>>() {}
       |               ^^^^^^^^^^^^^^^^^^^^
       |
       = help: consider removing the parameter
       = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#extra_unused_type_parameters
       = note: `-D clippy::extra-unused-type-parameters` implied by `-D clippy::all`

tests/test_from.rs

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