MRG: fix comment in _set_num_scaled #6176

Job	Run time
Check	29s
test (beta)	1m 31s
coverage	8m 51s
test (stable)	1m 19s
test_all_features	12m 24s
test (windows)	3m 56s
test (macos)	1m 16s
Lints (beta)	31s
Publish (on tags, dry-run otherwise)	5m 42s
Run tests under wasm32-wasi	1m 29s
Lints (stable)	28s
Check if wasm-pack builds a valid package for the sourmash crate	1m 21s
Check if cbindgen runs cleanly for generating the C headers	8m 5s
minimum_rust_version	6m 23s
	53m 45s

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