docs: use correct link to experiment script

[arthur-thuy]

Summary:

Features:

The hyperlink to file experiments/vgg_experiment.py did not work because the file does not exist (anymore). As such, I referred to the file vgg_mcdropout_cifar10.py which is already referenced in the README as a "complete experiment".

Checklist:

• Your code is documented (To validate this, add your module to tests/documentation_test.py).
• Your code is tested with unit tests.
• You moved your Issue to the PR state.

[Dref360]

Thank you very much!