Pass through rayon feature to ravif #1641

Job	Run time
Fuzz targets (cargo-fuzz)	53s
build_benchmarks	47s
Fuzz targets (afl)	2m 30s
cargo-deny	22s
cargo-semver-checks	36s
public_private_dependencies	24s
clippy	2m 1s
rustfmt	6s
test_avif_decoding	1m 21s
test_features	33s
test_other_archs (powerpc-unknown-linux-gnu)	3m 6s
test_features (default)	1m 57s
test_toolchains (1.70.0)	54s
test_other_archs (i686-unknown-linux-gnu)	1m 46s
test_features (rayon)	31s
test_toolchains (nightly)	1m 44s
test_features (avif)	58s
test_toolchains (beta)	1m 40s
test_features (bmp)	30s
test_features (dds)	50s
test_features (exr)	53s
test_features (ff)	47s
test_features (gif)	30s
test_features (hdr)	36s
test_features (ico)	52s
test_features (jpeg)	43s
test_features (png)	41s
test_features (pnm)	19s
test_features (qoi)	39s
test_features (tga)	19s
test_features (tiff)	34s
test_features (webp)	21s
	30m 43s

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