workflows/docker: fix missing arm64 digest

Signed-off-by: Patrick Linnane <[email protected]>

Author: p-linnane

.github/workflows/docker.yml

@@ -276,6 +276,7 @@ jobs:
           done <<<"$(jq --raw-output "${filter}" <<<"${TAGS}")"
 
           image_args=("ghcr.io/homebrew/ubuntu${VERSION}@sha256:$(<"${RUNNER_TEMP}/digests/${VERSION}-x86_64")")
+          image_args+=("ghcr.io/homebrew/ubuntu${VERSION}@sha256:$(<"${RUNNER_TEMP}/digests/${VERSION}-arm64")")
 
           attempts=0
           until docker buildx imagetools create "${tag_args[@]}" "${image_args[@]}"; do