Remove extraneous `#[warn(...)]` (#855) #2749

Job	Run time
Prime LFS Cache	7s
formatting	36s
cargo check (aarch64-android)	22s
cargo check (msrv) (windows-latest)	1m 14s
cargo clippy (wasm32)	2m 1s
cargo check (msrv) (macos-latest)	57s
cargo clippy (windows-latest)	4m 38s
cargo check (msrv) (ubuntu-latest)	1m 7s
cargo clippy (macos-latest)	2m 23s
cargo miri (unsafe tree_arena)	42s
cargo clippy (ubuntu-latest)	3m 32s
cargo test (wasm32)	19s
cargo check (msrv) (wasm32)	15s
cargo doc	2m 0s
typos	6s
cargo test (windows-latest)	2m 52s
cargo test (macos-latest)	2m 5s
cargo test (ubuntu-latest)	3m 21s
	28m 37s

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