Remove unused filter function

[matzew]

Proposed Changes

• 🧹 remove unused FilterWithNamespace function. Based on PR Improve trust bundle propagation #7665 all usage of the func was removed

Pre-review Checklist

• At least 80% unit test coverage
• E2E tests for any new behavior
• Docs PR for any user-facing impact
• Spec PR for any new API feature
• Conformance test for any change to the spec

Release Note

Docs

[matzew]

/assign @pierDipi

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.16%. Comparing base (8d8b6c9) to head (b191864).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8375      +/-   ##
==========================================
+ Coverage   64.14%   64.16%   +0.01%     
==========================================
  Files         389      388       -1     
  Lines       23335    23329       -6     
==========================================
  Hits        14969    14969              
+ Misses       7571     7565       -6     
  Partials      795      795              

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[matzew]

/retest

[creydr]

/lgtm

Having the same in pkg: https://github.com/knative/pkg/blob/f3ab5605e542aa36cf45056e58724ecf426202ef/reconciler/filter.go#L64-L71

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: creydr, matzew

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