[CI] use fixture to reduce download of cifar10 (#19039)
[CI] use fixture to reduce download of cifar10 (#19039)

* use fixture to reduce download of cifar10

* Update tests/python/unittest/test_io.py

Co-authored-by: Leonard Lausen <1828f72b2bad7e3ece38a8c55b121b66ea999efd@lausen.nl>

* fix

Co-authored-by: Leonard Lausen <1828f72b2bad7e3ece38a8c55b121b66ea999efd@lausen.nl>
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