[fix:tempelis] archive sig-security-assess* slack channels

[Priyankasaggu11929]

Fix for the failing post-community-tempelis-apply job: https://prow.k8s.io/view/gs/kubernetes-ci-logs/logs/post-community-tempelis-apply/1975546920612925440

 2025/10/07 13:01:13 This configuration cannot be applied against the current reality:
2025/10/07 13:01:13 Error 1: channel sig-security-assess-capi (C022K4F2W4W) not referenced in config.
2025/10/07 13:01:13 Error 2: channel sig-security-assess-vsphere-csi-driver (C04M4MFTJ6R) not referenced in config.
2025/10/07 13:01:13 We will not execute anything due to errors, but this what we would've done:
2025/10/07 13:01:13 Step 1: Set members of usergroup kubetail-maintainers (S08SBCW9U91) to [D08CF0BPYGG D08G3DBM3UN].
2025/10/07 13:01:13 Reconciliation failed: there were configuration errors 

Follow up #8645

cc: @tabbysable (for review)

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Priyankasaggu11929

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[Priyankasaggu11929]

/hold

for review

Hello @tabbysable, is the intended action to archive the two slack channels or delete them (in case of channel deletion, I think I will also need to check with slack admins) 🙂

[Priyankasaggu11929]

/assign @tabbysable