fix: Fix collection leak in querynode (#37061)

[bigsheeper]

Unref the removed L0 segment count.

issue: #36918

pr: #37061

[bigsheeper]

rerun ut

[codecov]

Codecov Report

Attention: Patch coverage is 89.18919% with 4 lines in your changes missing coverage. Please review.

Project coverage is 80.57%. Comparing base (6bc8aba) to head (87ec207).
Report is 6 commits behind head on 2.4.

Files with missing lines	Patch %	Lines
tests/integration/util_query.go	83.33%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##              2.4   #37079   +/-   ##
=======================================
  Coverage   80.56%   80.57%           
=======================================
  Files        1066     1066           
  Lines      165211   165242   +31     
=======================================
+ Hits       133110   133150   +40     
+ Misses      27763    27751   -12     
- Partials     4338     4341    +3     

Files with missing lines	Coverage Δ
internal/querynodev2/segments/collection.go	90.05% <100.00%> (+0.15%)	⬆️
internal/querynodev2/services.go	86.24% <100.00%> (-0.40%)	⬇️
tests/integration/suite.go	94.04% <100.00%> (+0.29%)	⬆️
tests/integration/util_query.go	86.34% <83.33%> (-0.40%)	⬇️

... and 32 files with indirect coverage changes

[czs007]

/approve
/lgtm

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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