chore: fix warnings, check-cfg #2427

Job	Run time
doctest	1m 11s
test ubuntu-latest stable --no-default-features	1m 7s
feature-checks	3m 11s
test ubuntu-latest stable	1m 16s
clippy	30s
no-std	14s
test ubuntu-latest nightly --no-default-features	1m 2s
wasm-unknown	39s
test ubuntu-latest nightly	1m 14s
wasm-wasi	55s
test ubuntu-latest 1.76 --no-default-features	48s
cfg-check	30s
test ubuntu-latest 1.76	1m 10s
test windows-latest stable --no-default-features	5m 28s
docs	56s
test windows-latest stable	5m 30s
fmt	15s
test windows-latest nightly --no-default-features	5m 14s
test windows-latest nightly	5m 0s
test windows-latest 1.76 --no-default-features	2m 18s
test windows-latest 1.76	3m 9s
test ubuntu-latest stable --all-features	1m 48s
test ubuntu-latest nightly --all-features	1m 37s
	45m 2s

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