wandb: Fix example rendering for docs

[EricCousineau-TRI]

What does this PR do?

Fixes doc rendering bug.

Before:
https://pytorch-lightning.readthedocs.io/en/stable/generated/pytorch_lightning.loggers.WandbLogger.html#pytorch_lightning.loggers.WandbLogger

After (local rendering, no style):

Before submitting

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• (N/A) Did you write any new necessary tests? (not for typos and docs)
• (N/A) Did you verify new and existing tests pass locally with your changes?
• (N/A) Did you update the CHANGELOG? (not for typos, docs, test updates, or internal minor changes/refactorings)

PR review

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Did you have fun?

Lol, more or less. Was investigating stuff like #981 tho :(

[codecov]

Codecov Report

Merging #5905 (a3ecf97) into master (fcfa7fa) will decrease coverage by 3%.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #5905    +/-   ##
=======================================
- Coverage      90%     88%    -3%     
=======================================
  Files         170     170            
  Lines       11784   11784            
=======================================
- Hits        10664   10362   -302     
- Misses       1120    1422   +302     

[carmocca]

LGTM!

Changed the base branch since we have blocked commits to master until the 1.3 release