[Machines] There is no "Remove" button for two network interface with same MAC address

Version-Release number of selected components (if applicable):
cockpit-machines-294-1.el9.noarch
cockpit-296-1.el9.x86_64
libvirt-dbus-1.4.1-5.el9.x86_64
libvirt-client-9.3.0-2.el9.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Create a VM with two network interfaces which have the same mac address

Try to delete one of them, but "Remove" button is disappeared .

Actual results:
See above.

Expected results:
There should be "Remove" button for user to delete the network interface with same MAC address.

Additional info:
If it's not allowed to add network interface with the same mac address , we can also limit it when adding, but once they exist, we should still can remove them.