ci: Improve cache when publishing (#360)

Author: sdn4z

.github/workflows/publish.yml

@@ -141,7 +141,9 @@ jobs:
           dockerfile: ./Dockerfile
           context: .
           image-name: elementsinteractive/twyn
-          cache-from: type=registry,ref=ghcr.io/elementsinteractive/twyn:buildcache-amd64,ref=ghcr.io/elementsinteractive/twyn:buildcache-arm64
+          cache-from: |
+            type=registry,ref=ghcr.io/elementsinteractive/twyn:buildcache-amd64
+            type=registry,ref=ghcr.io/elementsinteractive/twyn:buildcache-arm64
 
       - name: Delete old cache entries
         env: