A few minor clippy lints #2728

Job	Run time
msrv	49s
check-cfg	21s
docs	25s
minimal	20s
quickchecking	14s
rustfmt-clippy	31s
test-book	6s
test-expectations (ubuntu-latest)	45s
test-expectations (macos-latest)	48s
test-no-headers	35s
test (ubuntu-latest, 9.0, 0, 0, 0, 0)	1m 42s
test (ubuntu-latest, 9.0, 0, 0, 1, 0)	1m 34s
test (ubuntu-latest, 9.0, 0, 1, 0, 0)	1m 38s
test (ubuntu-latest, 9.0, 0, 1, 1, 0)	1m 38s
test (ubuntu-latest, 9.0, 1, 0, 0, 0)	2m 53s
test (ubuntu-latest, 9.0, 1, 0, 1, 0)	2m 11s
test (ubuntu-latest, 9.0, 1, 1, 0, 0)	2m 17s
test (ubuntu-latest, 9.0, 1, 1, 1, 0)	2m 21s
test (ubuntu-latest, 16.0, 0, 0, 0, 0)	4m 23s
test (ubuntu-latest, 16.0, 0, 0, 1, 0)	4m 10s
test (ubuntu-latest, 16.0, 0, 1, 0, 0)	4m 9s
test (ubuntu-latest, 16.0, 0, 1, 1, 0)	4m 19s
test (ubuntu-latest, 16.0, 1, 0, 0, 0)	5m 35s
test (ubuntu-latest, 16.0, 1, 0, 1, 0)	4m 47s
test (ubuntu-latest, 16.0, 1, 1, 0, 0)	4m 34s
test (ubuntu-latest, 16.0, 1, 1, 1, 0)	4m 49s
test (ubuntu-latest, 16.0, 0, 0, 1)	2m 28s
test (macos-latest, 16.0, 0, 0, 0)	1m 51s
success	1s
	1h 2m 14s

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