Fix ImageNet val loader to use val transform

[tridao]

What does this PR do?

Fix ImageNet val loader to use val transform instead of train transform

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• Did you write any new necessary tests? [not needed for typos/docs]
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Did you have fun?

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[ethanwharris]

LGTM 😃

[codecov]

Codecov Report

Merging #713 (dc743c7) into master (4046278) will not change coverage.
The diff coverage is n/a.

❗ Current head dc743c7 differs from pull request most recent head a6c763d. Consider uploading reports for the commit a6c763d to get more accurate results

@@           Coverage Diff           @@
##           master     #713   +/-   ##
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  Coverage   72.82%   72.82%           
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  Files         121      121           
  Lines        7550     7550           
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  Hits         5498     5498           
  Misses       2052     2052           

Flag	Coverage Δ
cpu	72.82% <ø> (ø)
pytest	72.82% <ø> (ø)

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