Ignore ignored_unit_patterns pedantic clippy lint in test suite

    warning: matching over `()` is more explicit
       --> tests/test_ensure.rs:710:34
        |
    710 |     let test = || Ok(ensure!(for _ in iter::once(()) {} != ()));
        |                                  ^ help: use `()` instead of `_`: `()`
        |
        = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#ignored_unit_patterns
        = note: `-W clippy::ignored-unit-patterns` implied by `-W clippy::pedantic`

tests/test_ensure.rs

@@ -4,6 +4,7 @@
     clippy::extra_unused_type_parameters,
     clippy::if_same_then_else,
     clippy::ifs_same_cond,
+    clippy::ignored_unit_patterns,
     clippy::items_after_statements,
     clippy::let_and_return,
     clippy::let_underscore_untyped,