Fix clippy lint in test suite #1482

Job	Run time
cargo-deny	20s
build_benchmarks	46s
Fuzz targets (afl)	2m 8s
Fuzz targets (cargo-fuzz)	1m 9s
cargo-semver-checks	22s
clippy	2m 14s
public_private_dependencies	24s
rustfmt	5s
test_avif_decoding	1m 22s
test_features	15s
test_other_archs (powerpc-unknown-linux-gnu)	2m 16s
test_features (default)	1m 46s
test_toolchains (1.67.1)	42s
test_other_archs (i686-unknown-linux-gnu)	1m 36s
test_features (rayon)	19s
test_toolchains (nightly)	1m 19s
test_features (avif)	56s
test_toolchains (beta)	1m 17s
test_features (bmp)	23s
test_features (dds)	22s
test_features (exr)	49s
test_features (ff)	17s
test_features (gif)	18s
test_features (hdr)	17s
test_features (ico)	27s
test_features (jpeg)	1m 22s
test_features (png)	22s
test_features (pnm)	41s
test_features (qoi)	17s
test_features (tga)	17s
test_features (tiff)	22s
test_features (webp)	28s
	25m 58s

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