delete global custom ports

[martinpitt]

Page: network/firewall

Cockpit can create and delete custom ports in a particular zone, but not global ones.

firewall-cmd --add-port=9119/tcp

This appears, but cannot be edited or removed:

Enhancement instead of bug, as that's just how the firewall page is designed (around zones). But at least deletion may be simple enough, the counterpart of firewall-cmd --remove-port=9119/tcp