[Backport 2.x] Modify the adding sample data part for timeline

[opensearch-trigger-bot]

Backport 48144c8 from #6919.

[github-actions]

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[codecov]

Codecov Report

Attention: Patch coverage is 92.59259% with 2 lines in your changes missing coverage. Please review.

Project coverage is 67.49%. Comparing base (bb0d30e) to head (54bc3d8).

Files	Patch %	Lines
src/core/server/saved_objects/import/utils.ts	90.47%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##              2.x    #6934   +/-   ##
=======================================
  Coverage   67.48%   67.49%           
=======================================
  Files        3442     3442           
  Lines       67884    67908   +24     
  Branches    11031    11035    +4     
=======================================
+ Hits        45812    45834   +22     
- Misses      19409    19410    +1     
- Partials     2663     2664    +1     

Flag	Coverage Δ
Linux_1	33.09% <14.28%> (-0.01%)	⬇️
Linux_2	55.18% <66.66%> (+<0.01%)	⬆️
Linux_3	45.25% <14.28%> (-0.02%)	⬇️
Linux_4	34.98% <85.18%> (+0.03%)	⬆️
Windows_1	33.11% <14.28%> (-0.01%)	⬇️
Windows_2	55.13% <66.66%> (+<0.01%)	⬆️
Windows_3	45.27% <14.28%> (-0.02%)	⬇️
Windows_4	34.98% <85.18%> (+0.03%)	⬆️

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