fix: fix bulk pack writer unstable unit test

[shaoting-huang]

related: #39601

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.74%. Comparing base (b3791a6) to head (a2dfed4).

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #39602      +/-   ##
==========================================
+ Coverage   80.14%   81.74%   +1.60%     
==========================================
  Files        1465     1163     -302     
  Lines      203091   176026   -27065     
==========================================
- Hits       162762   143900   -18862     
+ Misses      34526    26318    -8208     
- Partials     5803     5808       +5     

Components	Coverage Δ
Client	79.45% <ø> (ø)
Core	∅ <ø> (∅)
Go	81.84% <ø> (-0.05%)	⬇️

see 341 files with indirect coverage changes