publish-image: drop redundant release trigger

The 'release: published' trigger fired after the tag-push trigger for
the same release, causing mcp-publisher to attempt a duplicate publish
which the registry rejects with HTTP 400 'cannot publish duplicate
version'. The tag-push trigger alone covers our git tag -> gh release
create flow, so the second trigger was pure duplicate work.

Author: maciekaz

.github/workflows/publish-image.yml

@@ -17,8 +17,6 @@ on:
   push:
     tags: ['v*.*.*']
     branches: [main]
-  release:
-    types: [published]    # also fire when a Release is created from an existing tag (UI flow)
   workflow_dispatch: {}
 
 permissions: