Fix datasets in topomodelx' test workflow + Merge SNN

[ninamiolane]

What?

There is an issue upon loading the datasets from TopoNetX when testing TopoModelX through GitHub Actions. See details: https://github.com/pyt-team/TopoNetX/issues/195

We need to fix it.

Why?

Because the merge of TopoModelX's PR 98 is blocked by this: https://github.com/pyt-team/TopoModelX/pull/98

This PR has the implementation of the SNN model.

Where?

On TopoModelX, this might mean modifying the github workflow file for tests, which is: .github/workflows/test.yml

On TopoNetX, this might mean modifying how the datasets are loaded.

How?

Many tutorials manage to load and compute with datasets from TopoNetX. Get inspiration from this code and fix the dataset that is not working for the SNN PR 98.