Fix `<flat::View(Mut) as GenericImageView>::bounds` implementations #1012

Job	Run time
cargo-deny	31s
Fuzz targets (cargo-fuzz)	9m 38s
Fuzz targets (afl)	2m 28s
build_benchmarks	1m 20s
clippy	3m 42s
public_private_dependencies	27s
rustfmt	20s
test_avif	2m 22s
test_avif_decoding	1m 53s
test_big_endian	1m 53s
test_toolchains (1.61.0)	10m 13s
test_big_endian (default)	3m 21s
test_features	1m 17s
test_toolchains (nightly)	2m 50s
verify_msrv	4m 14s
test_big_endian (webp)	1m 48s
test_features (default)	2m 38s
test_toolchains (beta)	2m 8s
test_big_endian (webp-encoder)	2m 51s
test_features (gif)	53s
test_features (jpeg)	1m 1s
test_features (png)	1m 28s
test_features (tiff)	1m 20s
test_features (ico)	1m 21s
test_features (pnm)	1m 5s
test_features (tga)	57s
test_features (webp)	1m 14s
test_features (bmp)	59s
test_features (hdr)	57s
test_features (dxt)	50s
test_features (dds)	54s
test_features (farbfeld)	1m 7s
test_features (openexr)	1m 16s
test_features (jpeg_rayon)	1m 5s
test_features (webp-encoder)	2m 12s
	1h 14m 33s

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