Fix incorrect doc comment for as_mut_rgba32f (#2402) #1759

Job	Run time
cargo-deny	21s
build_benchmarks	42s
Fuzz targets (cargo-fuzz)	52s
Fuzz targets (afl)	2m 0s
cargo-semver-checks	28s
clippy	1m 59s
public_private_dependencies	23s
rustfmt	14s
test_avif_decoding	1m 23s
test_features	25s
test_other_archs (powerpc-unknown-linux-gnu)	2m 50s
test_features (default)	1m 52s
test_other_archs (i686-unknown-linux-gnu)	1m 27s
test_toolchains (1.70.0)	31s
test_features (rayon)	31s
test_features (avif)	1m 4s
test_toolchains (nightly)	1m 2s
test_features (bmp)	32s
test_toolchains (beta)	1m 17s
test_features (dds)	22s
test_features (exr)	39s
test_features (ff)	23s
test_features (gif)	25s
test_features (hdr)	23s
test_features (ico)	33s
test_features (jpeg)	26s
test_features (png)	32s
test_features (pnm)	24s
test_features (qoi)	24s
test_features (tga)	23s
test_features (tiff)	34s
test_features (webp)	31s
	25m 52s

Provide feedback