Fix checksum fuzzing target #905

Job	Run time
Smoke-test fuzzing targets	1m 57s
Clippy	19s
Smoke-test fuzzing targets (--no-default-features --features="c-allocator")	52s
QEMU build & test (stable, ubuntu-latest, s390x-unknown-linux-gnu, s390x-linux-gnu-gcc)	44s
Clippy (--no-default-features --features="c-allocator")	20s
Build and test (stable, ubuntu-latest, x86_64-unknown-linux-gnu)	52s
Smoke-test fuzzing targets (--no-default-features --features="rust-allocator")	52s
QEMU build & test (stable, ubuntu-latest, i686-unknown-linux-gnu, i686-linux-gnu-gcc)	41s
Build and test (msrv, ubuntu-latest, x86_64-unknown-linux-gnu)	1m 2s
Clippy (--no-default-features --features="rust-allocator")	20s
Build and test (beta, ubuntu-latest, x86_64-unknown-linux-gnu)	1m 0s
Smoke-test fuzzing targets (stable, macos-14, aarch64-apple-darwin)	2m 5s
dynamic library	14s
Build and test (stable, macos-latest, x86_64-apple-darwin)	1m 5s
Miri	2m 35s
Build and test (stable, macos-14, aarch64-apple-darwin)	1m 27s
wasm32	38s
Build and test (stable-x86_64-gnu, windows-2022, x86_64-pc-windows-gnu)	2m 9s
	19m 12s

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