fs: system: cleanup reflink

[efiop]

Per https://github.com/iterative/dvc-objects/pull/234/files#r1416499169

[codecov-commenter]

Codecov Report

Attention: 6 lines in your changes are missing coverage. Please review.

Comparison is base (8740236) 64.39% compared to head (58d6a3b) 63.44%.
Report is 1 commits behind head on main.

Files	Patch %	Lines
src/dvc_objects/fs/system.py	55.55%	4 Missing ⚠️
tests/benchmarks/test_fs.py	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #235      +/-   ##
==========================================
- Coverage   64.39%   63.44%   -0.96%     
==========================================
  Files          27       27              
  Lines        2039     2046       +7     
  Branches      323      324       +1     
==========================================
- Hits         1313     1298      -15     
- Misses        666      689      +23     
+ Partials       60       59       -1     

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