feat(ncu-ci): add --check-for-duplicates flag

[aduh95]

With this flag, the auto-start-ci workflow on nodejs/node would be less likely to start unnecessary CI runs.

[codecov]

Codecov Report

❌ Patch coverage is 80.76923% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 80.91%. Comparing base (2ea7b22) to head (9507a45).

Files with missing lines	Patch %	Lines
lib/ci/run_ci.js	80.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1035      +/-   ##
==========================================
- Coverage   80.94%   80.91%   -0.04%     
==========================================
  Files          39       39              
  Lines        4829     4847      +18     
==========================================
+ Hits         3909     3922      +13     
- Misses        920      925       +5     

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