should disable delete button for old interface policy when editing nncp

OCP Version: 4.14.0-0.ci.test-2023-07-20-111132-ci-ln-t0b7prb-latest
knmstate operator version: kubernetes-nmstate-operator.4.14.0-202307191212

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1. setup cluster
2. install knmstate operator
3. login web console as administrator, Networking -> NodeNetworkConfigurationPolicy, click create, select from form, create nncp with 1 interface policy, like bridge interface
4. edit the nncp, click delete button '-' to remove the old bridge interface policy

there is confirm window for deleting, although it does not work, the old interface policy will not be removed

should disable the delete button for the old interface policy, should not be allowed to remove it