Update example "Train a Vision Transformer on small datasets" from keras 2 to 3 version

[di-kan]

I am excited to contribute to this project. This is my first one. I have updated the example from keras 2 to keras 3.

[google-cla]

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[fchollet]

Sorry for the delay in review, this slipped through the cracks. The code looks good! Can you add the generated files?

[di-kan]

No worries at all. Of course, I will add the files.
Since I'm new in this, I converted another example (vit_small_ds.py) to version 3, but under the same branch (mine). Should I add those files as well?

[fchollet]

I converted another example (vit_small_ds.py) to version 3, but under the same branch (mine). Should I add those files as well

Yes, it's fine to do 2 examples in a single PR!