Pass through rayon feature to ravif #1627

Job	Run time
Fuzz targets (afl)	2m 29s
Fuzz targets (cargo-fuzz)	52s
cargo-deny	20s
build_benchmarks	45s
cargo-semver-checks	30s
public_private_dependencies	24s
clippy	2m 3s
rustfmt	5s
test_avif_decoding	1m 22s
test_other_archs (powerpc-unknown-linux-gnu)	2m 44s
test_features	27s
test_other_archs (i686-unknown-linux-gnu)	1m 43s
test_toolchains (1.67.1)	54s
test_features (default)	1m 57s
test_toolchains (nightly)	1m 28s
test_features (rayon)	37s
test_toolchains (beta)	1m 37s
test_features (avif)	1m 1s
test_features (bmp)	35s
test_features (dds)	56s
test_features (exr)	47s
test_features (ff)	30s
test_features (gif)	40s
test_features (hdr)	33s
test_features (ico)	39s
test_features (jpeg)	29s
test_features (png)	28s
test_features (pnm)	18s
test_features (qoi)	21s
test_features (tga)	18s
test_features (tiff)	26s
test_features (webp)	28s
	28m 46s

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