Tutorial update and dependency fix

[shenyangHuang]

This PR has a temporary fix for the IPU dependency issue. The installation on the README has been updated however the lightning version remains too old.

All current tutorials are able to run and tested.
Removed older tutorials:

• making gnn networks (for dgl only)
• using gnn layers (for dgl only)
• config ipu tutorial (outdated and current IPU configs are nested inside the same config files now), recommended to add newer IPU based tutorials

[zhiyil1230]

Hey thanks for the changes, I've tested this and I'm afraid pip install lightning gives lightning version of 2.0.4 which is not consistent with the 2.1.0 version that we have made changes with. The toymix config are not running as expcted and gives this error:
poptorch.poptorch_core.Error: In poptorch/source/dispatch_tracer/RegisterAtenOverloads.cpp:100: 'poptorch_cpp_error': There is no active dispatch

[zhiyil1230]

This works ok for me:
put lightning @ git+https://github.com/Lightning-AI/lightning@ca30fd7752582201a3966806c92e3acbbaf2a045
in a separate file named lightning.txt and run pip install with that separately. @shenyangHuang

[DomInvivo]

Let's ignore the unittest failing for now, it's the stanford datacenter that is down #365

[DomInvivo]

@shenyangHuang before merging, can you undo the deletion of the DGL-based tutorials? It's gonna be taken care in issue #374

[shenyangHuang]

• added lightning.txt and tested that the lightning is now installed to be 2.1.0.dev0
• added back the dgl tutorials, to be updated in Change the DGL-based tutorials #374

[zhiyil1230]

LGTM on the changes for lightning dependencies.