Sample nodes with timestamps equal to the seed node

[vid-koci]

Adjusts the code and docs for change 187 in pyg-lib. Temporal sampling should now sample nodes with the same timestamp as the seed nodes.

[codecov]

Codecov Report

Merging #6517 (7dbd43f) into master (77693c9) will not change coverage.
The diff coverage is 100.00%.

❗ Current head 7dbd43f differs from pull request most recent head 881ab28. Consider uploading reports for the commit 881ab28 to get more accurate results

@@           Coverage Diff           @@
##           master    #6517   +/-   ##
=======================================
  Coverage   85.68%   85.68%           
=======================================
  Files         406      406           
  Lines       22662    22662           
=======================================
  Hits        19418    19418           
  Misses       3244     3244           

Impacted Files	Coverage Δ
torch_geometric/loader/neighbor_loader.py	100.00% <ø> (ø)
torch_geometric/sampler/neighbor_sampler.py	91.56% <100.00%> (ø)

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