[BUG] Hydra fails to read paths on python 3.8

[vmoens]

We're having some odd behaviour with paths within hydra for the helper tests: https://github.com/pytorch/rl/actions/runs/8310294546/job/22742631224?pr=2008#step:11:17217

These lines have been introduced more than 2 years ago so it's unlikely that this is the issue.

Not being sure for how long torch will support 3.8 I'm moving the GPU tests to 3.10, but we'll still have one CPU job on 3.8 that will fail because of this.

cc @shagunsodhani

[vmoens]

I think this solved itself so closing for now