chore: drop OWNER files from ./test & ./hack

[dprotaso]

/assign @izabelacg

Productivity used to manage these in the past but really it should
be serving-writers reviewing these changes

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: dprotaso

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Needs approval from an approver in each of these files:

• hack/OWNERS [dprotaso]
• test/OWNERS [dprotaso]

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.43%. Comparing base (e3f29af) to head (02b0244).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #941   +/-   ##
=======================================
  Coverage   93.43%   93.43%           
=======================================
  Files          36       36           
  Lines        1249     1249           
=======================================
  Hits         1167     1167           
  Misses         69       69           
  Partials       13       13           

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[izabelacg]

/lgtm