fix link in examples README.md

[melvinebenezer]

🐛 Bug

Documentation in Examples: The link to Lightning AI tutorial on CIFAR is broken

Command

To Reproduce

Steps to reproduce the behavior:

1. go to examples/README.md
2. section on ViT
3. click on "this Pytorch Lightning" hyperlink

Expected behavior

correct link https://lightning.ai/docs/pytorch/stable/notebooks/lightning_examples/cifar10-baseline.html