build: fix clippy lints and MSRV check #3601

Job	Run time
Check	38s
Check if cbindgen runs cleanly for generating the C headers	1m 40s
coverage	8m 2s
Lints (beta)	44s
Lints (stable)	49s
minimum_rust_version	2m 23s
Publish (dry-run)	46s
test (beta)	4m 32s
test (stable)	4m 10s
test (windows)	6m 44s
test (macos)	5m 41s
test_all_features	20m 32s
Run tests under wasm32-wasi	2m 1s
Check if wasm-pack builds a valid package for the sourmash crate	1m 55s
	1h 0m 37s

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