pcx: Switch test images out #1684

Job	Run time
Fuzz targets (cargo-fuzz)	50s
build_benchmarks	45s
cargo-deny	20s
Fuzz targets (afl)	2m 2s
cargo-semver-checks	39s
clippy	2m 1s
public_private_dependencies	22s
rustfmt	11s
test_avif_decoding	1m 24s
test_other_archs (powerpc-unknown-linux-gnu)	2m 31s
test_other_archs (i686-unknown-linux-gnu)	1m 39s
test_features	26s
test_toolchains (1.70.0)	27s
test_features (default)	1m 49s
test_toolchains (nightly)	1m 22s
test_features (rayon)	37s
test_toolchains (beta)	1m 33s
test_features (avif)	1m 4s
test_features (bmp)	32s
test_features (dds)	28s
test_features (exr)	46s
test_features (ff)	27s
test_features (gif)	29s
test_features (hdr)	30s
test_features (ico)	35s
test_features (jpeg)	44s
test_features (pcx)	26s
test_features (png)	38s
test_features (pnm)	28s
test_features (qoi)	26s
test_features (tga)	29s
test_features (tiff)	41s
test_features (webp)	38s
	28m 19s

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