refactor(configuration): simplify boolean check

[cjihrig]

Which problem is this PR solving?

A disabled check in the configuration package is a little confusing to read. The value can be true, false, or undefined. Instead of checking for a truthy or false value, the code can be simplified to only a check for undefined.

Fixes # N/A

Short description of the changes

This commit updates the confusing check to a single undefined check.

Type of change

None of these.

How Has This Been Tested?

• Test suite

Checklist:

• Followed the style guidelines of this project
• Unit tests have been added
• Documentation has been updated

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.40%. Comparing base (8ff6b76) to head (3eafadf).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #6158   +/-   ##
=======================================
  Coverage   95.40%   95.40%           
=======================================
  Files         317      317           
  Lines        9427     9427           
  Branches     2178     2178           
=======================================
  Hits         8994     8994           
  Misses        433      433           

Files with missing lines	Coverage Δ
...al/packages/configuration/src/FileConfigFactory.ts	96.85% <100.00%> (ø)

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[raphael-theriault-swi]

LGTM but I'd still like @maryliag to give her approval :)

[otelbot]

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