Remove legacy_datasets var from skimage.data._registry #7676
Description
First discussed in https://github.com/scikit-image/scikit-image/pull/7660/files#r1914963651.
It looks like legacy_datasets
scikit-image/skimage/data/_registry.py
Lines 1 to 8 in bbbfcdb
is only ever used to create legacy_registry
scikit-image/skimage/data/_registry.py
Lines 182 to 184 in bbbfcdb
And it seems the latter is never used. Is there any reason not to remove them?
Also it seems to me that the comment is incorrect. When I check the scikit-image v0.15 wheel, there are many more datasets in the wheel that are not listed in legacy_datasets.
Included in v0.15 wheel but not in legacy_datasets
_blobs_3d_fiji_skeleton.tif
astronaut_GRAY_hog_L1.npy
astronaut_GRAY_hog_L2-Hys.npy
block.png
bw_text.png
bw_text_skeleton.npy
checker_bilevel.png
chessboard_GRAY_U16.tif
chessboard_GRAY_U16B.tif
chessboard_GRAY_U8.npy
chessboard_GRAY_U8.npz
chessboard_RGB_U8.npy
chessboard_RGB_U8.npz
diamond-matlab-output.npz
disk-matlab-output.npz
foo3x5x4indexed.png
gray_morph_output.npz
green_palette.png
mssim_matlab_output.npz
multi.fits
orb_descriptor_positions.txt
palette_color.png
palette_gray.png
rank_filter_tests.npz
rough-wall.png
simple.fits
truncated.jpg