Replace MIPS targets with PowerPC #947

Job	Run time
test_toolchains (1.61.0)	36s
test_toolchains (nightly)	2m 12s
test_toolchains (beta)	2m 10s
Fuzz targets (afl)	2m 44s
clippy	4m 34s
Fuzz targets (cargo-fuzz)	6m 47s
build_benchmarks	1m 26s
public_private_dependencies	28s
test_avif	2m 14s
test_avif_decoding	2m 9s
test_big_endian	1m 58s
test_big_endian (default)	3m 39s
test_big_endian (webp)	1m 58s
test_big_endian (webp-encoder)	3m 17s
test_features	35s
test_features (default)	1m 56s
test_features (gif)	42s
test_features (jpeg)	48s
test_features (png)	1m 5s
test_features (tiff)	49s
test_features (ico)	46s
test_features (pnm)	44s
test_features (tga)	41s
test_features (webp)	40s
test_features (bmp)	40s
test_features (hdr)	42s
test_features (dxt)	42s
test_features (dds)	37s
test_features (farbfeld)	34s
test_features (openexr)	1m 21s
test_features (jpeg_rayon)	1m 10s
test_features (webp-encoder)	1m 13s
cargo-deny	32s
rustfmt	21s
verify_msrv	3m 3s
	55m 53s

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