chore: correct build arg syntax (#75)

Author: SamMorrowDrums

.github/workflows/docker-publish.yml

@@ -80,8 +80,8 @@ jobs:
           cache-from: type=gha
           cache-to: type=gha,mode=max
           platforms: linux/amd64,linux/arm64
-          build-args:
-            VERSION: ${{ github.ref_name }}
+          build-args: |
+            VERSION=${{ github.ref_name }}
 
       # Sign the resulting Docker image digest except on PRs.
       # This will only write to the public Rekor transparency log when the Docker