Not overriding symlink at release-registry when publishing

[philipphofmann]

When the release-registry already contains a symlink for the specified version craft fails to publish the release. I would expect that it overrides the symlink with the JSON for the specified release.

Steps to reproduce with sentry-cocoa:

1. craft prepare 5.1.10
2. Create a symlink for 5.1.10.json in release-registry for cocoa.
3. craft publish 5.1.10 --target registry
4. Craft fails with Error: Version file for "5.1.10" already exists. Aborting.

This is related to getsentry/sentry-release-registry#27

[tonyo]

As mentioned in the offline discussion, this in not something we should change in craft, I believe. This error actually helped to uncover the issue we have with the tooling in release-registry.
@philipphofmann lmk if you still think that we should change this behavior.