Fix norm in examples and dmon_pool

[lightaime]

This PR fixed the deprecated batch_norm to norm in examples and dmon_pool.

[codecov]

Codecov Report

Merging #4959 (12c2b62) into master (bac7021) will decrease coverage by 0.01%.
The diff coverage is 100.00%.

❗ Current head 12c2b62 differs from pull request most recent head 1de2669. Consider uploading reports for the commit 1de2669 to get more accurate results

@@            Coverage Diff             @@
##           master    #4959      +/-   ##
==========================================
- Coverage   82.72%   82.70%   -0.02%     
==========================================
  Files         330      330              
  Lines       17905    17905              
==========================================
- Hits        14812    14809       -3     
- Misses       3093     3096       +3     

Impacted Files	Coverage Δ
torch_geometric/nn/dense/dmon_pool.py	98.00% <100.00%> (ø)
torch_geometric/nn/models/mlp.py	94.44% <0.00%> (-4.17%)	⬇️

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