[docs] Fix docstring of LightningModule._auto_collect_args()

[akihironitta]

What does this PR do?

Fixes # (issue)

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[codecov]

Codecov Report

Merging #4585 (9586c7e) into master (e01190e) will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff           @@
##           master   #4585   +/-   ##
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  Coverage      93%     93%           
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  Files         116     116           
  Lines        8833    8833           
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  Hits         8235    8235           
  Misses        598     598           

[ydcjeff]

Thank you! Akihi

[awaelchli]

too many ducks visited these docs!