MRG: fix benchmark code & a few other small issues from pyOpenSci review #4218

Job	Run time
coverage	10m 20s
coverage	9m 19s
Check	25s
Check	25s
Lints (beta)	31s
Lints (beta)	31s
minimum_rust_version	8m 7s
minimum_rust_version	8m 7s
Publish (dry-run)	6m 1s
Publish (dry-run)	6m 1s
Lints (stable)	24s
Lints (stable)	24s
test (beta)	1m 28s
test (beta)	1m 28s
test (stable)	1m 18s
test (stable)	1m 18s
test_all_features	10m 41s
test_all_features	10m 41s
Run tests under wasm32-wasi	1m 18s
Run tests under wasm32-wasi	1m 18s
test (windows)	3m 30s
test (windows)	3m 30s
test (macos)	3m 19s
test (macos)	3m 19s
Check if wasm-pack builds a valid package for the sourmash crate	1m 14s
Check if wasm-pack builds a valid package for the sourmash crate	1m 14s
Check if cbindgen runs cleanly for generating the C headers	50s
Check if cbindgen runs cleanly for generating the C headers	50s
	1h 37m 51s

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