main/postmarketos-ui-sxmo-de-sway: don't install bonsai on aarch64

bonsai is only available on x86_64 on Alpine v3.17 as Hare is only is available for x86_64 on that release of Alpine.

See https://pkgs.alpinelinux.org/packages?name=hare&branch=v3.17&repo=&arch=&maintainer=

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@StacyHarper @anjandev @proycon Does this look fine?