Remove support for ARM64 platforms in build workflow

We cannot currently test _any_ ARM64 platforms under qemu because qemu
cannot currently support iptables.  See multiarch/qemu-user-static#191
for more details.

.github/workflows/build.yml

@@ -179,7 +179,10 @@ jobs:
       matrix:
         architecture:
           - amd64
-          - arm64
+          # We cannot currently test _any_ ARM64 platforms under qemu
+          # because qemu cannot currently support iptables:
+          # https://github.com/multiarch/qemu-user-static/issues/191
+          # - arm64
         platform:
           # Amazon Linux 2023 does not appear to offer ufw
           # - amazonlinux2023-systemd

README.md

@@ -7,6 +7,11 @@ An Ansible role for installing [Uncomplicated
 Firewall](https://wiki.ubuntu.com/UncomplicatedFirewall?action=show&redirect=UbuntuFirewall)
 (UFW).
 
+> [!NOTE]
+> We cannot currently test *any* ARM64 platforms under `qemu` because
+> [`qemu` cannot currently support
+> `iptables`](https://github.com/multiarch/qemu-user-static/issues/191).
+
 ## Requirements ##
 
 None.