[v1.16] fix: verify argocd instance matches namespace label on appset cleanup

[jgwest]

What type of PR is this?
/kind bug

What does this PR do / why we need it:
Backport of argoproj-labs/argocd-operator#1971

[svghadi]

/lgtm
/approve

[openshift-ci]

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[jgwest]

/retest

FAIL: kuttl/harness/1-005_validate_route_tls

[svghadi]

/retest

[openshift-ci]

@jgwest: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
ci/prow/v4.17-kuttl-parallel	ac02134	link	true	/test v4.17-kuttl-parallel

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[jgwest]

/retest

[jgwest]

Merging as all other tests appear to be passing, and same issue as last time: #1025 (comment)