Add missing Genius dataset

[Padarn]

This PR addresses part of the request in #4569 to add the missing datasets from LINKX.

This PR adds only the Genius dataset that seemed to be missing from PyG.

[codecov]

Codecov Report

Merging #4570 (631fdd7) into master (926b5dc) will decrease coverage by 0.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #4570      +/-   ##
==========================================
- Coverage   82.91%   82.79%   -0.12%     
==========================================
  Files         315      315              
  Lines       16596    16594       -2     
==========================================
- Hits        13760    13739      -21     
- Misses       2836     2855      +19     

Impacted Files	Coverage Δ
torch_geometric/nn/conv/utils/typing.py	81.25% <0.00%> (-17.50%)	⬇️
torch_geometric/io/tu.py	93.58% <0.00%> (-2.57%)	⬇️
torch_geometric/nn/models/mlp.py	98.41% <0.00%> (-1.59%)	⬇️
torch_geometric/transforms/gdc.py	78.17% <0.00%> (-1.02%)	⬇️
torch_geometric/data/dataset.py	96.80% <0.00%> (-0.80%)	⬇️
torch_geometric/nn/conv/rgat_conv.py	83.76% <0.00%> (-0.53%)	⬇️
torch_geometric/graphgym/utils/comp_budget.py	15.51% <0.00%> (+0.51%)	⬆️

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[Padarn]

Hey @rusty1s sorry for the earlier WIP - I was still figuring out how I thought it best to add these datasets.

I decided it was best to add them to the existing LINKXDataset as in my original PR - the reason being that these datasets are modified from the original datasets, and I thought it would be confusing if we named them individually.

I will add the other datasets in another PR if you're okay with this approach.

[rusty1s]

Thanks @Padarn. I agree with you. This approach sounds perfect to me!