zeroize_derive: fixup test suite [1.4] #1062

Job	Run time
cross (powerpc-unknown-linux-gnu, stable)	28s
cross (powerpc-unknown-linux-gnu, 1.56.0)	6m 40s
aarch64 (aarch64-unknown-linux-gnu, 1.59.0)	1m 3s
aarch64 (aarch64-unknown-linux-gnu, stable)	48s
build (stable, thumbv7em-none-eabi)	19s
build (1.56.0, wasm32-unknown-unknown)	5m 45s
build (1.56.0, thumbv7em-none-eabi)	5m 59s
build (1.56.0, armv7a-none-eabi)	5m 45s
build (stable, wasm32-unknown-unknown)	11s
test (x86_64-unknown-linux-gnu, ubuntu-latest, 1.56.0)	37s
test (x86_64-apple-darwin, macos-latest, stable)	4s
build (stable, armv7a-none-eabi)	19s
test (x86_64-unknown-linux-gnu, ubuntu-latest, stable)	21s
minimal-versions / minimal-versions	20s
test (x86_64-apple-darwin, macos-latest, 1.56.0)	20s
test (x86_64-pc-windows-msvc, windows-latest, 1.56.0)	5m 1s
test (x86_64-pc-windows-msvc, windows-latest, stable)	15s
test (i686-unknown-linux-gnu, ubuntu-latest, 1.56.0, sudo apt update && sudo apt install gcc-mult...	30s
test (i686-unknown-linux-gnu, ubuntu-latest, stable, sudo apt update && sudo apt install gcc-mult...	25s
	35m 10s

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