collab: Always use newest anthropic model version (#15978)

When Anthropic releases a new version of their models, Zed AI users
should always get access to the new version even when using an old
version of zed.

Co-Authored-By: Thorsten <thorsten@zed.dev>

Release Notes:

- N/A

Co-authored-by: Thorsten <thorsten@zed.dev>