okd: cleanup rule disabling `kyverno-policy-prevent-mgmt-cluster-delete`

The kyverno-policy-prevent-mgmt-cluster-delete unit currently has an enabled_conditions items disabling it if OKD cabpoa unit is enabled.

kyverno-policy-prevent-mgmt-cluster-delete:
...
    enabled_conditions:
...
    - '{{ not (tuple . "cabpoa" | include "unit-enabled")  }}'

This had been done in !2654 (merged) to workaround a case where a Kyverno results in failures on CAPI control plane resources because Kyverno CRD cache is outdated.

I believe that special case for cabpoa should be removed:

• I believe that !3145 (merged) fixes it
• I don't think the problem was specific to OKD/CABPOA in the first place

/cc @jianzzha