Update stable Rust, fix clippy lints #723

Job	Run time
cargo clippy (wasm32)	1m 21s
cargo check (msrv) (wasm32)	1m 15s
cargo clippy (windows-latest)	1m 48s
cargo check (msrv) (windows-latest)	1m 49s
cargo clippy (macos-latest)	1m 1s
cargo check (msrv) (macos-latest)	1m 29s
cargo doc	20s
formatting	13s
cargo clippy (ubuntu-latest)	1m 9s
cargo check (msrv) (ubuntu-latest)	1m 15s
cargo test (windows-latest)	58s
cargo test (wasm32)	33s
typos	4s
cargo test (macos-latest)	48s
cargo test (ubuntu-latest)	34s
	14m 37s

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