Drop torch_sparse dependency in transforms.* and sampler.*

[rusty1s]

No description provided.

[codecov]

Codecov Report

Merging #6138 (ec2a362) into master (7a785a0) will decrease coverage by 1.89%.
The diff coverage is 86.95%.

@@            Coverage Diff             @@
##           master    #6138      +/-   ##
==========================================
- Coverage   86.25%   84.36%   -1.90%     
==========================================
  Files         363      363              
  Lines       20483    20480       -3     
==========================================
- Hits        17667    17277     -390     
- Misses       2816     3203     +387     

Impacted Files	Coverage Δ
torch_geometric/sampler/neighbor_sampler.py	67.05% <0.00%> (-2.87%)	⬇️
torch_geometric/transforms/sign.py	36.00% <0.00%> (-4.00%)	⬇️
torch_geometric/sampler/hgt_sampler.py	100.00% <100.00%> (ø)
torch_geometric/sampler/utils.py	85.41% <100.00%> (+1.41%)	⬆️
torch_geometric/transforms/add_metapaths.py	98.44% <100.00%> (-0.02%)	⬇️
...ch_geometric/transforms/add_positional_encoding.py	98.27% <100.00%> (ø)
torch_geometric/transforms/feature_propagation.py	97.14% <100.00%> (ø)
torch_geometric/transforms/gdc.py	79.39% <100.00%> (-0.11%)	⬇️
torch_geometric/transforms/line_graph.py	100.00% <100.00%> (ø)
torch_geometric/transforms/rooted_subgraph.py	98.82% <100.00%> (ø)
... and 24 more

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