fix: source lib.sh in docker-buildx-push for tagging version (#5024)

ci/steps/docker-buildx-push.sh

@@ -3,6 +3,9 @@ set -euo pipefail
 
 main() {
   cd "$(dirname "$0")/../.."
+  # ci/lib.sh sets VERSION so it's available to ci/release-image/docker-bake.hcl
+  # to push the VERSION tag.
+  source ./ci/lib.sh
 
   # NOTE@jsjoeio - this script assumes that you've downloaded
   # the release-packages artifact to ./release-packages before