OCI artifact tag gets updated on push to main

[chrede88]

The newest release tag (0.23.2) gets updated on push to main via the release-publish workflow. This is not great as the digest of the tag is also updated, which triggers redeployment of the chart for people running the cloudnative operator (even with the release pinned to the tag). I don't know which CI workflows should run on pushes to main, but releasing charts shouldn't be done unless a new release is ready.