Dont guess at mappings when values are static

[kddejong]

Issue #, if available:
fix #3873
Description of changes:

• When doing language extension transform don't guess at a mapping value when the FindInMap values are static

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[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 93.82%. Comparing base (8454bc9) to head (a9cc1ac).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...fnlint/template/transforms/_language_extensions.py	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3875      +/-   ##
==========================================
- Coverage   93.83%   93.82%   -0.02%     
==========================================
  Files         365      365              
  Lines       12515    12516       +1     
  Branches     2571     2572       +1     
==========================================
- Hits        11744    11743       -1     
  Misses        426      426              
- Partials      345      347       +2     

Flag	Coverage Δ
unittests	93.78% <75.00%> (-0.02%)	⬇️

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