Clippy fixes #430

Job	Run time
build (stable, serde, ubuntu-latest)	1m 44s
build (stable, serde, macos-latest)	3m 40s
build (stable, serde, windows-latest)	3m 22s
build (stable, base64, ubuntu-latest)	1m 36s
build (stable, base64, macos-latest)	1m 40s
build (stable, base64, windows-latest)	2m 48s
build (stable, default, ubuntu-latest)	1m 29s
build (stable, default, macos-latest)	46s
build (stable, default, windows-latest)	3m 26s
build (nightly, serde, ubuntu-latest)	1m 48s
build (nightly, serde, macos-latest)	1m 59s
build (nightly, serde, windows-latest)	2m 3s
build (nightly, base64, ubuntu-latest)	1m 41s
build (nightly, base64, macos-latest)	2m 42s
build (nightly, base64, windows-latest)	2m 3s
build (nightly, simd_backend, ubuntu-latest)	1m 41s
build (nightly, simd_backend, macos-latest)	1m 53s
build (nightly, default, ubuntu-latest)	1m 35s
build (nightly, default, macos-latest)	2m 1s
build (nightly, default, windows-latest)	2m 3s
	42m 0s

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