Fix/wandb log summary

[martins0n]

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• Did you read the contribution guide?
• Did you update the docs? We use Numpy format for all the methods and classes.
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• Examples / docs / tutorials / contributors update
• Bug fix (non-breaking change which fixes an issue)
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[codecov-commenter]

Codecov Report

Merging #535 (4278133) into master (dda1455) will decrease coverage by 0.04%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master     #535      +/-   ##
==========================================
- Coverage   87.29%   87.24%   -0.05%     
==========================================
  Files         118      118              
  Lines        5698     5701       +3     
==========================================
  Hits         4974     4974              
- Misses        724      727       +3     

Impacted Files	Coverage Δ
etna/loggers/wandb_logger.py	33.33% <0.00%> (-1.29%)	⬇️

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[iKintosh]

Why do we log only once? Instead of several times as we did before?

[martins0n]

Because wandb.summary is one final state,
and one wandb.log -- is one state vs multiple wandb.log -- multiple states.