Update nn.aggr documentation

[rusty1s]

No description provided.

[codecov]

Codecov Report

Merging #5099 (a43a3d3) into master (2efd97a) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head a43a3d3 differs from pull request most recent head 64e7f3e. Consider uploading reports for the commit 64e7f3e to get more accurate results

@@            Coverage Diff             @@
##           master    #5099      +/-   ##
==========================================
- Coverage   83.00%   83.00%   -0.01%     
==========================================
  Files         333      333              
  Lines       18368    18365       -3     
==========================================
- Hits        15246    15243       -3     
  Misses       3122     3122              

Impacted Files	Coverage Δ
torch_geometric/nn/aggr/attention.py	100.00% <ø> (ø)
torch_geometric/nn/aggr/base.py	95.74% <ø> (ø)
torch_geometric/nn/aggr/gmt.py	100.00% <ø> (ø)
torch_geometric/nn/aggr/lstm.py	100.00% <ø> (ø)
torch_geometric/nn/aggr/multi.py	100.00% <ø> (ø)
torch_geometric/nn/aggr/equilibrium.py	97.70% <100.00%> (-0.08%)	⬇️

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