fix: Fix get binary vector from chunk cache (#28866)

[bigsheeper]

The way of getting binary vector size is wrong. This PR will fix it.

issue: #28865

pr: #28866

[codecov]

Codecov Report

Merging #28884 (bcc9a0c) into 2.3 (ce8219f) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

Additional details and impacted files

@@            Coverage Diff             @@
##              2.3   #28884      +/-   ##
==========================================
- Coverage   82.00%   81.99%   -0.01%     
==========================================
  Files         820      820              
  Lines      118623   118622       -1     
==========================================
- Hits        97274    97266       -8     
- Misses      18132    18138       +6     
- Partials     3217     3218       +1     

Files	Coverage Δ
internal/core/src/segcore/SegmentSealedImpl.cpp	78.74% <0.00%> (+0.12%)	⬆️

... and 13 files with indirect coverage changes

[czs007]

/approve
/lgtm

[sre-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: bigsheeper, czs007

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