fix: upload cifar10 and cifar100 datasets

[ghsanti]

The modifications to get_file, and removing the deprecated untar need an extra directory name to be accessed.
Other possible solutions were provided by myself an others in the linked Issue.

I did a demo here: Colab, also tested on Windows.

The commit that produced the issue seems to be this one.

Maybe @ashep29 or @mehtamansi29 have an opinion.

Note that it's just one commit, somehow VSCode managed to duplicate it.

Closes #20180

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[ghsanti]

i've signed cla already, idk why it fails.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 0% with 4 lines in your changes missing coverage. Please review.

Project coverage is 79.37%. Comparing base (19ba3d1) to head (1fc5f38).
Report is 181 commits behind head on master.

Files with missing lines	Patch %	Lines
keras/src/datasets/cifar10.py	0.00%	2 Missing ⚠️
keras/src/datasets/cifar100.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #20185      +/-   ##
==========================================
- Coverage   79.37%   79.37%   -0.01%     
==========================================
  Files         501      501              
  Lines       47348    47350       +2     
  Branches     8695     8695              
==========================================
  Hits        37582    37582              
- Misses       8009     8011       +2     
  Partials     1757     1757              

Flag	Coverage Δ
keras	79.22% <0.00%> (-0.01%)	⬇️
keras-jax	62.49% <0.00%> (-0.01%)	⬇️
keras-numpy	57.67% <0.00%> (-0.01%)	⬇️
keras-tensorflow	63.88% <0.00%> (-0.01%)	⬇️
keras-torch	62.54% <0.00%> (-0.01%)	⬇️

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[fchollet]

Thanks for the fix!