Enable zram swap for gitlab.archlinux.org

Boxy seems to randomly restart after running out of memory. We do not
yet know the reason behind the increased memory usage, but zram might
help a bit.

host_vars/gitlab.archlinux.org/misc

 ansible_port: 2222
 filesystem: btrfs
+enable_zram_swap: true
 additional_addresses: ["213.133.111.6/32", "2a01:4f8:222:174c::2/64"]
 wireguard_address: 10.0.0.5
 wireguard_public_key: EbZisS0fwM6B8Nkugy1lyox+A8L13hniucVIPVCK5R0=