chore: fix some warnings #3152

Job	Run time
check no-default-features	29s
test stable --no-default-features	51s
test stable	52s
test no_std	26s
test stable --all-features	1m 23s
test beta --no-default-features	2m 24s
test beta	2m 27s
check serde	20s
check std	30s
test beta --all-features	2m 31s
test nightly --no-default-features	2m 15s
clippy	1m 16s
docs	1m 13s
test nightly	2m 27s
test nightly --all-features	2m 27s
fmt	12s
	22m 3s

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