Remove concurrency features

[sushichop]

Need to be careful about introducing concurrency features until Swift 6.

[codecov]

Codecov Report

Merging #39 (87f8013) into main (182de01) will decrease coverage by 0.12%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main      #39      +/-   ##
==========================================
- Coverage   95.93%   95.81%   -0.13%     
==========================================
  Files          11       11              
  Lines         418      406      -12     
==========================================
- Hits          401      389      -12     
  Misses         17       17              

Impacted Files	Coverage Δ
Sources/Puppy/FileLogger.swift	92.04% <ø> (-0.96%)	⬇️

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