Use ko label filter instead of removing KnativeCertificate yaml

[ReToCode]

Changes

• Followup for Update net-istio to use KnativeCertificate instead of control-protocol secret #1221
• Removing the file results in the KnativeCertificate not being in the release manifest: knative/serving@a420015#diff-845c4618eefc690238aaab455d8f1b79ffd5c30eec4c2f5b50da9b57017b39a8L588
• Use ko label filter instead of removing KnativeCertificate yaml

/assign @skonto

[knative-prow]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (e6e6cb7) 81.66% compared to head (239908d) 81.84%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1224      +/-   ##
==========================================
+ Coverage   81.66%   81.84%   +0.17%     
==========================================
  Files          19       19              
  Lines        1680     1680              
==========================================
+ Hits         1372     1375       +3     
+ Misses        220      218       -2     
+ Partials       88       87       -1     

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[skonto]

/lgtm

[ReToCode]

/test integration-tests