Switch from voxpupuli/ferm to voxpupuli/nftables for firewalling #255

Job	Run time
Puppet / Static validations	25s
Puppet / 8 (Ruby 3.2)	45s
Puppet / Distro Puppet - Archlinux rolling	1m 29s
Puppet / 7 (Ruby 2.7)	53s
Puppet / Puppet 8 - Ubuntu 20.04	2m 45s
Puppet / Puppet 7 - Ubuntu 20.04	2m 29s
Puppet / Puppet 8 - Ubuntu 22.04	2m 43s
Puppet / Puppet 7 - Ubuntu 22.04	2m 17s
Puppet / Puppet 8 - Debian 11	2m 4s
Puppet / Puppet 7 - Debian 11	1m 54s
Puppet / Test suite	0s
	17m 44s

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