zeroize_derive: fixup test suite [1.4] #1060

Job	Run time
cross (powerpc-unknown-linux-gnu, 1.56.0)	51s
aarch64 (aarch64-unknown-linux-gnu, 1.59.0)	48s
aarch64 (aarch64-unknown-linux-gnu, stable)	34s
cross (powerpc-unknown-linux-gnu, stable)	36s
build (1.56.0, wasm32-unknown-unknown)	13s
minimal-versions / minimal-versions	40s
test (i686-unknown-linux-gnu, ubuntu-latest, 1.56.0, sudo apt update && sudo apt install gcc-mult...	15s
build (1.56.0, thumbv7em-none-eabi)	25s
build (1.56.0, armv7a-none-eabi)	13s
build (stable, armv7a-none-eabi)	13s
build (stable, wasm32-unknown-unknown)	11s
build (stable, thumbv7em-none-eabi)	9s
test (x86_64-apple-darwin, macos-latest, stable)	11s
test (x86_64-apple-darwin, macos-latest, 1.56.0)	1s
test (x86_64-pc-windows-msvc, windows-latest, stable)	2s
test (x86_64-unknown-linux-gnu, ubuntu-latest, 1.56.0)	26s
test (x86_64-pc-windows-msvc, windows-latest, 1.56.0)	16s
test (x86_64-unknown-linux-gnu, ubuntu-latest, stable)	14s
test (i686-unknown-linux-gnu, ubuntu-latest, stable, sudo apt update && sudo apt install gcc-mult...	27s
	6m 45s

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