github: Trigger image workflow on release.published

Updates #12753

Author: bep

.github/workflows/image.yml

@@ -1,10 +1,8 @@
 name: Build Docker image
 
 on:
-  push:
-    tags:
-      - "*"
-  workflow_dispatch:
+  release:
+    types: [published]
 permissions:
   packages: write