Remove old unused_tuple_struct_fields lint

    error: lint `unused_tuple_struct_fields` has been renamed to `dead_code`
      --> src/main.rs:38:5
       |
    38 |     unused_tuple_struct_fields,
       |     ^^^^^^^^^^^^^^^^^^^^^^^^^^ help: use the new name: `dead_code`
       |
    note: the lint level is defined here
      --> src/main.rs:6:5
       |
    6  |     warnings,
       |     ^^^^^^^^
       = note: `#[deny(renamed_and_removed_lints)]` implied by `#[deny(warnings)]`

tests/smoke-test/src/main.rs

@@ -35,7 +35,6 @@
     unused_lifetimes,
     unused_qualifications,
     unused_results,
-    unused_tuple_struct_fields,
     variant_size_differences
 )]