Fix renamed let_underscore_drop lint
Fix renamed let_underscore_drop lint

    error: lint `clippy::let_underscore_drop` has been renamed to `let_underscore_drop`
     --> tests/test.rs:9:5
      |
    9 |     clippy::let_underscore_drop,
      |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `let_underscore_drop`
      |
      = note: `-D renamed-and-removed-lints` implied by `-D warnings`

serde-rs/json