Rename internal serialization function

[gerlero]

No description provided.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 86.66667% with 2 lines in your changes missing coverage. Please review.

Project coverage is 88.61%. Comparing base (223f19d) to head (b093373).
Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
foamlib/_files/_serialization.py	84.61%	2 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #240   +/-   ##
=======================================
  Coverage   88.61%   88.61%           
=======================================
  Files          16       16           
  Lines        1239     1239           
=======================================
  Hits         1098     1098           
  Misses        141      141           

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