[cherry-pick] fix 20496

[wy65701436]

fixes #20496

Harbor will reserve one SBOM accessory artifact for each subject artifact. Ensure all existing SBOMs are removed before generating the next set.

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Comprehensive Summary of your change

Issue being fixed

Fixes #(issue)

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[codecov]

Codecov Report

Attention: Patch coverage is 63.63636% with 4 lines in your changes are missing coverage. Please review.

Please upload report for BASE (release-2.11.0@14f9af0). Learn more about missing BASE report.

Additional details and impacted files

@@                Coverage Diff                @@
##             release-2.11.0   #20509   +/-   ##
=================================================
  Coverage                  ?   66.23%           
=================================================
  Files                     ?     1045           
  Lines                     ?   113463           
  Branches                  ?     2842           
=================================================
  Hits                      ?    75155           
  Misses                    ?    34204           
  Partials                  ?     4104           

Flag	Coverage Δ
unittests	66.23% <63.63%> (?)

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Files	Coverage Δ
src/pkg/scan/sbom/sbom.go	52.72% <63.63%> (ø)