Remove old unused_tuple_struct_fields lint

[dtolnay]

unused_tuple_struct_fields no longer exists in Rust 1.77 since rust-lang/rust#118297. It has been subsumed by dead_code.

This is causing the "smoke test" in CI to fail.

bitflags/.github/workflows/rust.yml

Lines 38 to 39 in 586d819

	- name: Smoke test
	run: cargo run --manifest-path tests/smoke-test/Cargo.toml

$ cargo run --manifest-path tests/smoke-test/Cargo.toml

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)]`

[KodrAus]

Thanks @dtolnay!