fix lint complaints about case-fold builder

[timbray]

No description provided.

[github-actions]

⚠️ Performance Alert ⚠️

Possible performance regression was detected for benchmark 'Go Benchmark'.
Benchmark result of this commit is worse than the previous benchmark result exceeding threshold 1.20.

Benchmark suite	Current: 6bc1d6c	Previous: 78e2ec8	Ratio
BenchmarkCityLots	6866 ns/op 829 B/op 34 allocs/op	5592 ns/op 773 B/op 31 allocs/op	1.23
BenchmarkCityLots - ns/op	6866 ns/op	5592 ns/op	1.23
Benchmark_JsonFlattner_Evaluate_ContextFields	1221 ns/op 96 B/op 8 allocs/op	726.2 ns/op 56 B/op 4 allocs/op	1.68
Benchmark_JsonFlattner_Evaluate_ContextFields - ns/op	1221 ns/op	726.2 ns/op	1.68
Benchmark_JsonFlattner_Evaluate_ContextFields - B/op	96 B/op	56 B/op	1.71
Benchmark_JsonFlattner_Evaluate_ContextFields - allocs/op	8 allocs/op	4 allocs/op	2

This comment was automatically generated by workflow using github-action-benchmark.

[codecov-commenter]

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.59%. Comparing base (db62f53) to head (6bc1d6c).
Report is 1 commits behind head on main.

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Additional details and impacted files

@@           Coverage Diff           @@
##             main     #348   +/-   ##
=======================================
  Coverage   96.59%   96.59%           
=======================================
  Files          19       19           
  Lines        1940     1940           
=======================================
  Hits         1874     1874           
  Misses         37       37           
  Partials       29       29           

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