refactor: Replace _.flatMap usage

[JonasMatos0]

Addresses: #7747

[codecov]

Codecov Report

Merging #9948 (016cf25) into master (6087fa3) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 016cf25 differs from pull request most recent head d20c30d. Consider uploading reports for the commit d20c30d to get more accurate results

@@           Coverage Diff           @@
##           master    #9948   +/-   ##
=======================================
  Coverage   86.18%   86.19%           
=======================================
  Files         330      330           
  Lines       13004    13007    +3     
=======================================
+ Hits        11208    11211    +3     
  Misses       1796     1796           

Impacted Files	Coverage Δ
lib/classes/PluginManager.js	94.69% <100.00%> (+0.03%)	⬆️
lib/plugins/aws/invokeLocal/index.js	68.90% <100.00%> (+0.08%)	⬆️

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[pgrzesik]

Thank you @JonasMatos0 - it looks good 👍